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Chapter 9

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Biotechnology : Principles
and Processes
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◎ CBSE SQP
¥ for 2025 board
š 2025 SQP 1
Eco R1 cuts the DNA between bases G and A only
when the sequence of GAATTC is present. The
number of nucleotides present in the resultant
sticky ends that will be formed in each of the two
strands of DNA after this enzyme cuts the DNA
will be:
Vector DNA Foreign DNA
(a) 1 & 5 5 & 1
(b) 2 & 4 4 & 2 www.cbse.page

(c) 2 & 5 5 & 2

(d) 3 & 4 4 & 3

Answer A 1 Marks

Option (a) is correct

š 2025 SQP 2
Assertion (A) : DNA fragments can be isolated by
Gel electrophoresis on the basis of their size.

Reason (R) : The larger the fragment size, the

faster it moves.

(a) Both Assertion (A) and Reason (R) are true and
Reason (R) is the correct explanation of the
Assertion (A).
(b) Both Assertion (A) and Reason (R) are true, but
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Reason (R) is not the correct explanation of the

Assertion (A).
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true.

Answer A 1 Marks

(c) Assertion (A) is true, but Reason (R) is false

š 2025 SQP 3
A culture plate of Lactobacillus shows
blue-coloured colonies and colourless colonies.
Explain the principle involved in the formation of
such variance in the colour of colonies.

Answer A 2 Marks

¥ The variation in colour of colonies is due to

the principle of insertional inactivation.
¥ In this, a recombinant DNA is inserted within
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the coding sequence of an enzyme,

β-galactosidase. This results into inactivation
of the enzyme, which is referred to as
insertional inactivation.
¥ The presence of a chromogenic substrate
gives blue-coloured colonies if the plasmid in
the bacteria does not have an insert.
¥ Presence of insert results into insertional
inactivation of the β - galactosidase and the
colonies do not produce any colour, these are
 identified as recombinant colonies.

š 2025 SQP 4
Explain how PCR technique can be used for
amplification of a small amount of DNA template.

Answer A 3 Marks

PCR stands for Polymerase Chain Reaction. In this

reaction, multiple copies of the gene (or DNA) of
interest are synthesised in vitro using two sets of
primers (small chemically synthesised www.cbse.page

oligonucleotides that are complementary to the

regions of DNA) and the enzyme DNA polymerase.
The enzyme extends the primers using the
nucleotides provided in the reaction and the
genomic DNA as template.

If the process of replication of DNA is repeated

many times, the segment of DNA can be amplified
to approximately billion times, i.e., 1 billion copies
are made. Such repeated amplification is achieved
by the use of a thermostable DNA polymerase
(isolated from a bacterium, Thermus aquaticus),
which remains active during the high temperature
induced denaturation of double stranded DNA.
The amplified fragment if desired can now be used
to ligate with a vector for further cloning.

Each cycle has three steps:

(i) Denaturation (ii) Annealing (iii) Extensions

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if possible then draw diagram

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◎ 57/5 All Sets

¥ 2024 March
š 2024 PYQ 5 ¥ 57/5, Set 1
Which one of the following statements is correct in
the context of observing DNA separation by
agarose gel electrophoresis?
(A) DNA can be seen in visible light.
(B) DNA can be seen without staining in visible
light.
(C) Ethidium bromide stained DNA can be seen in
visible light.
(D) Ethidium bromide stained DNA can be seen
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under UV light.

Answer A 1 Marks

Option (D) is correct.

Ethidium bromide intercalates between the base
pairs of DNA molecules and when exposed to UV
light, it fluorescence, emitting visible light. This
fluorescence allows the visualisation of DNA
bands appears orange in the gel.
š 2024 PYQ 6 ¥ 57/5, Set 1
If the sequence of nitrogen bases of the coding
strand in a transcription unit is 5’ – ATGAATG – 3’,
the sequence of bases in its RNA transcript would
be
(A) 5’ – AUGAAUG – 3’ (B) 5’ – UACUUAC – 3’
(C) 5’ – CAUUCAU – 3’ (D) 5’ – GUAAGUA – 3’

Answer A 1 Marks

Option (A) is correct. Given the coding strand

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sequence: 5’–ATGAATG–3’, the corresponding

RNA transcript sequence would be 5’– AUGAAUG
–3’ as Thymine replaced by Uracil.

š 2024 PYQ 7 ¥ 57/5, Set 1

↓
5’ – G A A T T C – 3’
3’ – C T T A A↑ G – 5’
(a) Name the restriction enzyme that recognises
the given specific sequence of bases. What are
such sequence of bases referred to as ? 1 Marks
(b) What are the arrows in the given figure
indicating ? Write the result obtained
thereafter. 1 Marks

Answer A 2 Marks

(a) Restriction enzyme: EcoRI

Palindrome / palindromic nucleotide
sequences.
(b) Indicates the site at which EcoRI makes a cut
in the two strands of DNA / restriction sites or
recognition sites of EcoRI, thereafter gives rise
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to “sticky ends.”

š 2024 PYQ 8 ¥ 57/5, Set 1

(i) Draw a schematic diagram of the cloning

vector pBR 322 and label (1) Bam HI site (2)
gene for ampicillin resistance (3) ’ori’ (4) ’rop’
gene.
(ii) State the role of ’rop’ gene.
(iii) A cloning vector does not have a selectable
 marker. How will it affect the process of
cloning?
(iv) Why is insertional inactivation preferred over
the use of selectable markers in cloning
vectors?

Answer A 5 Marks

(i) Schematic diagram of pBR322

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(ii) The rop gene encodes a small regulatory

 protein, Rop (repressor of primer), in pBR322
plasmids. The primary role of this protein is to
control the copy number of the plasmid
within the bacterial host.
(iii) The absence of a selectable marker in a
cloning vector complicates the process of
cloning by making it difficult to distinguish
between cells that have incorporated the
vector with the desired DNA insert and those
that haven’t. Selectable markers, like
antibiotic resistance genes, help in the growth
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and selection of transformed cells, simplifying

the process by allowing the isolation of only
those cells that have successfully taken up the
vector.
(iv) Insertional inactivation is favoured over the
use of selectable markers in cloning vectors
because it facilitates the straightforward
identification of recombinant plasmids
without requiring extra selection procedures.
 With insertional inactivation, the cloning
vector harbours a reporter gene interrupted by
the insertion site for DNA fragments.
Successful insertion of a DNA fragment
disrupts the reporter gene, causing a loss of
function that can be visually observed. This
approach streamlines the cloning process and
eliminates the necessity for antibiotic
selection, making it more convenient and
economical.

š 2024 PYQ 9
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¥ 57/5, Set 2
Which one of the following enzymes a fungal cell
should be treated with to get the DNA along with
other macro molecules released from it?
(A) Isozymes
(B) Cellulose
(C) Ribonuclease
(D) Chitinase

Answer A 1 Marks
Option (D) is correct. Chitinase is the enzyme that
degrades chitin, a major component of the fungal
cell wall. Treating fungal cells with chitinase helps
to break down the cell wall, releasing DNA along
with other macro molecules from the cell.

š 2024 PYQ 10 ¥ 57/5, Set 2

(a) Why must a cell be made ’competent’ in
biotechnology experiments? How does
calcium ion help in doing so?
(b) State the role of "biolistic gun" in www.cbse.page

biotechnology experiments.

Answer A 3 Marks

(a) In biotechnology experiments, the cells must

be made competent so that they can take up
the hydrophilic DNA molecule inside them
from the external medium. Treatment of
bacterial cells with divalent calcium cations
makes them competent and helps them to
take up the DNA through the pores in the cell
 wall.
(b) Biolistic gene or gene gun is a method of
introducing alien DNA into the plants cells. In
this method, the host cells are bombarded
with high–velocity micro–particles of gold or
tungsten coated with DNA molecules,
facilitating genetic modification without the
need for complex tissue culture

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◎ 57/4 All Sets

¥ 2024 March
š 2024 PYQ 11 ¥ 57/4, Set 1
The ‘molecular scissors’ fall in the category of :
(A) Cleaving enzyme
(B) Endonuclease
(C) Exonuclease
(D) Restriction enzymes

Answer A 1 Marks

(D) Restriction enzymes

š 2024 PYQ 12 ¥ 57/4, Set 1

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Assertion (A) : Plasmids are autonomously

replicating circular extra-chromosomal DNA.

Reason (R) : Plasmids are usually present in

Eukaryotic cells.

(a) Both Assertion (A) and Reason (R) are true and
Reason (R) is the correct explanation of the
Assertion (A).
(b) Both Assertion (A) and Reason (R) are true,
but Reason (R) is not the correct explanation
 of the Assertion (A).
(c) Assertion (A) is true but Reason (R) is false.
(d) Assertion (A) is false but Reason (R) is true.

Answer A 1 Marks

(c) Assertion (A) is true but Reason (R) is false.

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š 2024 PYQ 13 ¥ 57/4, Set 1
Study the steps shown below, that are carried
during a specific technique :

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(A) Identify the steps ‘A’ and ‘D’ in the diagram.

(B) What does ‘B’ represent ?
(C) Write what is ‘C’ ? Name its source organism.
(D) Mention the use of this technique in molecular
diagnostics.
 Answer A 3 Marks

(A) A- Denaturation , D- Extension

(B) B- Primers
(C) C- Taq polymerase , Source- Thermus
aquaticus
(D) Use- Detection of AIDS/Cancer/ Genetic
disorder/ Amplification of mutated gene/
Early diagnosis of disease [Any one]

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š 2024 PYQ 14 ¥ 57/4, Set 2

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The schematic representation as above is showing

the linking of two DNA fragments.
(a) Name ‘A’ and ‘B’ fragments.
(b) Write the ‘palindrom’ recognised by EcoRI.
(c) Where does EcoRI cut the palindrome ? Write
the events followed thereafter to form a
recombinant DNA.

Answer A 3 Marks
(a) A – vector DNA,
B is foreign DNA / Desired DNA / Alien DNA
′ ′
(b) 5 G A A T T C 3
′ ′
3 CTTAAG5
(c) It cuts the DNA between bases G and A only ,
It give rise to sticky ends of ‘A’ DNA and ‘B’
DNA which is joined by ligase enzyme to form
recombinant DNA.

š 2024 PYQ 15 ¥ 57/4, Set 3

Draw a schematic diagram of the E.coli vector
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pBR322 and mark the following in it :

(a) ori
(b) rop
(c) ampicillin resistant gene
(d) tetracycline-resistant gene
(e) restriction site Bam HI
(f) restriction site EcoRI

Answer A 3 Marks
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◎ 57/3 All Sets

¥ 2024 March
š 2024 PYQ 16 ¥ 57/3, Set 1
Which native plasmid did Stanley Cohen and
Herbert Boyer use for the construction of the first
recombinant DNA ?

(a) Salmonella typhimurium

(b) Streptococcus pneumoniae
(c) Escherichia coli
(d) Haemophilus influenzae

Answer A 1 Marks
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(a) Salmonella typhimurium

š 2024 PYQ 17 ¥ 57/3, Set 1
Which one of the following represents the correct
annealing of primers to the DNA to be amplified
in the PCR ?

(a)

(b) www.cbse.page

(c)

(d)

Answer A 1 Marks

Option (b) is correct

š 2024 PYQ 18 ¥ 57/3, Set 1
With reference to the set−ups (A, B and C) given
below, of the electrophoretic separation of a
mixture of DNA fragments of varied lengths,
answer the questions that follow :

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(a) In which one of the two Set-ups, A or B, would

you see the DNA fragments separated and
why? Justify your answer.
(b) In Set−up C, which one of the two, I / II, are
the bands of longer fragments of DNA ? Justify
your answer.

Answer A 2 Marks
(a) Set up A, DNA fragments being negatively
charged move towards the anode on applying
the electric field
(b) I, Smaller fragment will move faster as
compared to longer fragments of DNA / longer
fragments of DNA will move slower as
compared to smaller fragments of DNA.

š 2024 PYQ 19 ¥ 57/3, Set 1

Case Based Question
Read the passage given below and answer the
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questions that follow.

In recombinant DNA technology, restriction
enzymes are used as they recognize and cut DNA
within a specific recognition sequence. BamH I is
one such restriction enzyme which binds at the
recognition sequence 5’ G−G−A−T−C−C 3’ and
cleaves this sequence between G and G on each
strand, whereas Alu I binds at the recognition
sequence 5’ A−G−C−T 3’ and cleaves these
sequences between G and C on each strand.
(a) If Alu I is used to cut the given DNA strand,
how many DNA fragments would be formed ?
Write the sequence of each fragment formed
with its polarity.

(b) Which one of the two restriction enzymes

BamH I or Alu I will preferably be used on the
same given DNA strand to make a
recombinant DNA molecule and why ?
(c) After binding to the two strands of the double
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helix DNA, where specifically does the

restriction enzyme act to cut the two strands
of DNA ? Write the specific term used for the
specific nucleotide sequences of DNA
recognised by a restriction endonuclease.
OR
(c) Write the specific sequence of DNA segment
recognised by the restriction endonuclease
EcoRI.
 Answer A 4 Marks

(a) 3 / Three fragments

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(b) Alu I, Alu I site is present in the given sequence

and BamH I site is not given.
(c) Sugar phosphate backbone
Palindrome sequence / recognition site /
restriction site
OR
′ ′
(c) 5 G−A−A−T−T−C 3
′ ′
3 C −T−T−A−A−G 5
š 2024 PYQ 20 ¥ 57/3, Set 2
For the replication of the first recombinant DNA,
Stanley Cohen and Herbert Boyer used the DNA
polymerase of :

(a) Thermus aquaticus

(b) Salmonella typhimurium
(c) Escherichia coli
(d) Haemophilus influenzae

Answer A 1 Marks
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(c) Escherichia coli

š 2024 PYQ 21 ¥ 57/3, Set 3
The linking of the antibiotic resistance gene with
the plasmid vector of Salmonella typhimurium by
Stanley Cohen and Herbert Boyer was made
possible by the enzyme :

(a) Taq polymerase

(b) DNA ligase
(c) Restriction endonuclease
(d) β - galactosidase
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Answer A 1 Marks

(b) DNA ligase

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◎ 57/2 All Sets

¥ 2024 March
š 2024 PYQ 22 ¥ 57/2, Set 1
Which one of the following is not a feature of
plasmids ?

(A) Circular
(B) Self-replicating
(C) Single stranded
(D) Extra-chromosomal

Answer A 1 Marks

(C) Single stranded www.cbse.page

š 2024 PYQ 23 ¥ 57/2, Set 1

Assertion (A) : Specific enzymes are used to
degrade the cell wall in organisms to isolate the
DNA from the cell.
Reason (R) : Fungal cell wall is degraded by the
enzyme cellulase.

(a) Both Assertion (A) and Reason (R) are true and
Reason (R) is the correct explanation of the
Assertion (A).
(b) Both Assertion (A) and Reason (R) are true,
but Reason (R) is not the correct explanation
of the Assertion (A).
(c) Assertion (A) is true but Reason (R) is false.
(d) Assertion (A) is false but Reason (R) is true.

Answer A 1 Marks

(c) Assertion (A) is true but Reason (R) is false.

š 2024 PYQ 24 ¥ 57/2, Set 1

Write the role of ’ori’ and restriction site in the
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cloning vector pBR322.

Answer A 2 Marks

Ori – site where replication starts/Responsible for

controlling the copy number of the linked DNA.

Restriction site – Site of ligation of alien DNA or

foreign DNA or desirable DNA to the vector.
š 2024 PYQ 25 ¥ 57/2, Set 1

(i) Why should a cell be made competent to take

up an alien DNA ? How can a bacterial cell be
made competent using calcium ions? Explain.
(ii) (1) State the importance of gel
electrophoresis in biotechnology.
(2) Explain the principle on which this
technique works.
(3) Mention why ethidium bromide is used in
this technique. www.cbse.page

Answer A 5 Marks

(i) § DNA is a hydrophilic molecule and cannot

pass through the cell membrane.
§ A bacterial cell is made competent by
treating the bacterial cell with a specific
concentration of a divalent cation such as
calcium, which increases efficiency with
which the DNA enters through pores in its
cell wall/This creates certain transient
 pores in its cell and increases the
efficiency of the cell to take up DNA.
(ii) (1) Separation of DNA fragments.
(2) DNA fragments are negatively charged
molecules, they can be separated
according to their size by forcing them to
move toward the anode under an electric
field through agarose gel.
(3) To stain the DNA to visualize by exposure
to UV radiation.
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š 2024 PYQ 26 ¥ 57/2, Set 2

Which of the following is not required for PCR ?

(A) Restriction endonuclease

(B) Taq Polymerase
(C) Primer
(D) DNA segment

Answer A 1 Marks

(A) Restriction endonuclease

š 2024 PYQ 27 ¥ 57/2, Set 2
Assertion (A) : In genetic engineering, antibiotic
genes are used as selectable markers.

Reason (R) : Selectable markers help us to identify

transformants from non-transformants.

(a) Both Assertion (A) and Reason (R) are true and
Reason (R) is the correct explanation of the
Assertion (A).
(b) Both Assertion (A) and Reason (R) are true,
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but Reason (R) is not the correct explanation

of the Assertion (A).
(c) Assertion (A) is true but Reason (R) is false.
(d) Assertion (A) is false but Reason (R) is true.

Answer A 1 Marks

(A) Both Assertion (A) and Reason (R) are true and
Reason (R) is the correct explanation of the
Assertion (A).
š 2024 PYQ 28 ¥ 57/2, Set 2
How is a restriction endonuclease named? Explain
with the help of a suitable example.

Answer A 2 Marks

In EcoRI

First letter ‘E’ comes from the genus,

the second two ‘co’ letters from the species,

letter ‘R’ – is derived from the name of strain,

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Roman number ‘I’- indicates the order in which

the enzyme is isolated.

š 2024 PYQ 29 ¥ 57/2, Set 3

Which one of the following is not used as a vector
for rDNA technology ?

(A) Plasmid (C) Bacteriophage

(B) Bacterial cell (D) Retrovirus

Answer A 1 Marks
(B) Bacterial cell

š 2024 PYQ 30 ¥ 57/2, Set 1

Assertion (A) : A recombinant DNA which is
inserted within the coding sequence of
β-galactosidase does not produce blue coloured
colonies when treated with a chromogenic
substrate.

Reason (R) : Insertional inactivation occurs when

a recombinant DNA is introduced in the coding
sequence of the enzyme. www.cbse.page

(a) Both Assertion (A) and Reason (R) are true and
Reason (R) is the correct explanation of the
Assertion (A).
(b) Both Assertion (A) and Reason (R) are true,
but Reason (R) is not the correct explanation
of the Assertion (A).
(c) Assertion (A) is true but Reason (R) is false.
(d) Assertion (A) is false but Reason (R) is true.
 Answer A 1 Marks

(a) Both Assertion (A) and Reason (R) are true and
Reason (R) is the correct explanation of the
Assertion (A).

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◎ 2024 March
¥ 57/1 All Sets
š 2024 PYQ 31 ¥ 57/1, Set 1
Restriction Endonuclease Hind II always cuts DNA
molecules at a particular point by recognising a
specific sequence of :
(A) Six base pairs
(B) Four base pairs
(C) Seven base pairs
(D) Three base pairs

Answer A 1 Marks
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(A) Six base pairs

š 2024 PYQ 32 ¥ 57/1, Set 1

(i) Explain the convention for naming EcoRI.

(ii) With the help of an illustration only, show the
action of EcoRI on a DNA Polynucleotide.

Answer A 3 Marks

In EcoRI (comes from Escherichia coli RY13)

§ -E represent Genus Escherichia ,
§ -co represent species coli,
§ -R represent RY 13 strain,
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§ -I represent order in which the enzyme were

isolated from that strain of bacteria.
š 2024 PYQ 33 ¥ 57/1, Set 1

Case Based Question

Study the diagram given below that shows the
steps involved in the procedure of selecting
transformed bacteria and answer the questions
that follow :

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(a) Identify the colony that has got transformed.

Justify your answer.
(b) What are the sites in a plasmid called where
ampicillin and tetracycline resistance genes
are inserted ? State their role in genetic
 engineering.
(c) Name two enzymes playing an important role
in genetic engineering.
OR
(c) State the role of -galactosidase in insertional
inactivation.

Answer A 5 Marks

(a) Colony 4 is transformed with plasmid

containing recombinant DNA, as they will not
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show resistance towards tetracycline.

(b) Award 2 marks to each student .
(c) Restriction endonuclease / ligase / Taq DNA
Polymerase
OR
(c) Insertional inactivation of gene encoding for
β-galactosidase will lead to colorless bacterial
colonies (recombinant)
š 2024 PYQ 34 ¥ 57/1, Set 2
Using a DNA template, how many new DNA
molecules would be generated after 10 cycles of
amplification in PCR ?
(A) 512
(B) 1024
(C) 2048
(D) 256

Answer A 1 Marks
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(B) 1024
š 2024 PYQ 35 ¥ 57/1, Set 3
Which one of the following bacteria were used by
Stanley Cohen and Herbert Boyer to accomplish
the construction of the first rDNA ?
(A) Agrobacterium tumefaciens
(B) Mycobacterium sp.
(C) E. coli
(D) Salmonella typhimurium

Answer A 1 Marks
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(D) Salmonella typhimurium

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◎ 2024 March
¥ 57(B)
š 2024 PYQ 36 ¥ 57(B), Set 1
Read the passage given below and answer the
questions that follow.

"Biotechnology is based on the manipulation of

the genes either by addition of a desirable gene or
deletion of an undesirable gene from the genome
of an organism. This genetic engineering is carried
out keeping the welfare of the humans in mind."

(a) Write the specific sequence of nucleotides that

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are recognised by EcoRI on a DNA segment.
Where in this specific sequence does the
enzyme make a ’cut’ in the sugar-phosphate
backbone of the DNA?
(b) Mention how a "transformant" can be
distinguished from a "non-transformant"
bacterial colony in a culture medium.
OR
(b) List the five tools generally used in genetic
engineering.
(c) Name a synthetic/engineered vector. Why
does it have multiple restriction sites in it?

Answer A 5 Marks

5‘ GAATTC 3’

3‘ CTTAAG 5’,
Enzyme makes a cut between G and A nucleotide /

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(b) The non-transformants will lose resistance to

specific antibiotics, and will not form colony,
but transformants will show resistance to
specific antibiotics, and will form colony
OR
(b) Restriction enzymes, polymerase enzymes,
 ligases, vectors, host organism
(any four correct tools)
(c) § pBR322 / any other correct example,
§ To provide flexibility in the choice of
restriction endonucleases / to facilitate
insertion of foreign DNA into the vector at
restriction site

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◎ 2023 March
¥ 57/5 All Sets
š 2023 PYQ 37 ¥ 57/5, Set 1
Given below is the restriction site of a restriction
endonuclease Pst-I and the cleavage sites on a
DNA molecule.

Choose the option that gives the correct resultant

fragments by the action of the enzyme Pst-I.

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(a)

(b)

(c)

(d)

Answer A 1 Marks
(d)

š 2023 PYQ 38 ¥ 57/5, Set 1

Assertion (A) : Synthetic oligonucleotide
polymers are used during Annealing in a PCR.

Reason (R) : The primers bind to the double

stranded DNA at their complementary regions.

(a) Both Assertion (A) and Reason (R) are true and
Reason (R) is the correct explanation of the
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Assertion (A).
(b) Both Assertion (A) and Reason (R) are true,
but Reason (R) is not the correct explanation
of the Assertion (A).
(c) Assertion (A) is true and Reason (R) is false.
(d) Assertion (A) is false and Reason (R) is true.

Answer A 1 Marks

(c) (A) is true, but (R) is false.

š 2023 PYQ 39 ¥ 57/5, Set 1

(a) Write the scientific name of the source

organism of the themostable DNA polymerase
used in PCR.
(b) State the advantage of using Thermostable
DNA polymerase.

Answer A 2 Marks

(a) Thermus aquaticus

(b) Thermostable DNA polymerase remains www.cbse.page

active during the high temperature induced

denaturation of double stranded DNA / It is
not required to be added every time after
denaturation in every cycle.

š 2023 PYQ 40 ¥ 57/5, Set 1

Bioreactors are the containment vehicles of any
biotechnology-based production process. For
large scale production and for economic reasons
the final success of biotechnological process
depends on the efficiency of the bioreactor.

Answer the following questions w.r.t. the given

paragraph:
(i) List the operational guidelines that must be
adhered to achieve optimisation of the
bioreactor system. Enlist any four.
(ii) Mention the phase of the growth we refer to in
the statement "Optimisation of growth and
metabolic activity of the cells".
(iii) Is the biological product formed in the
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bioreactor suitable for the intended use

immediate? Give reason in support of your
answer.
OR
(i) EcoRI has played very significant role in
r-DNA technology.

(I) Explain the convention for naming EcoRI.

(II) Write the recognition site and the cleavage
sites of this restriction endonuclease.
(ii) What are the protruding and hanging
stretches of DNA produced by these
restriction enzymes called? Describe their role
in formation of r-DNA.

Answer A 5 Marks

(i) Optimum growth conditions : Temperature ,

pH , Substrate , Salts , Vitamins , Oxygen
(ii) Log phase / Exponential phase
(iii) § No
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§ it needs separation and purification /

down-streaming process / quality control
testing / needs to be formulated with
suitable preservatives / clinical trials.
OR
(I) E - Genus

co – Species

R – Strain

I – Order of isolation of enzyme

(II) Recognition site –
5’GAATTC 3’
3’CTTAAG 5’
Cleavage site – Between G and A from both
sides
or

(ii) § Sticky ends www.cbse.page

§ Sticky ends form hydrogen bonds with

their complimentary cut counterparts,
this stickiness facilitates the action of the
enzyme DNA ligase.

š 2023 PYQ 41 ¥ 57/5, Set 2

(a) State the principle involved in separation of
DNA fragments using gel electrophoresis,
(b) How are DNA fragments visualised once they
are separated by gel electrophoresis?
 Answer A 2 Marks

(a) Negatively charged DNA fragments move

towards anode under electric field, DNA
fragments separate (resolve) according to their
size due to sieving effect of agarose gel.
(b) The DNA fragments can be visualised as
orange coloured bands in a ethidium bromide
stained gel, exposed to UV light.

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 www.cbse.page

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◎ 2023 March
¥ 57/3 All Sets
š 2023 PYQ 42 ¥ 57/3, Set 1
The given schematic illustration shows three steps
P’ Q’ and R’ of the polymerase chain reaction.

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Which of the following statements are correct with

reference to the illustration given above?
(i) Step ’P’ is showing denaturation at low
temperature.
(ii) Step ’Q’ is a denaturation of DNA strand at
high temperature, followed by annealing.
(iii) Step ’R’ is an extension of DNA in presence of
thermostable DNA polymerase.
(iv) Step ’Q’ is extension with two sets of primers.
(a) (i) and (iii) only (c) (ii) only
(b) (ii) and (iii) only (d) (i) only

Answer A 1 Marks

(b) (ii) and (iii) only

š 2023 PYQ 43 ¥ 57/3, Set 1

Answer the following questions with respect to
recombinant DNA technology:
(i) Why is plasmid considered to be an important
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tool in rDNA technology? From where can
plasmids be isolated? (Any two sources)
(ii) Explain the role of ’ori’ and selectable marker
in a cloning vector.
(iii) "r-DNA technology cannot proceed without
restriction endonuclease." Justify.

Answer A 5 Marks

(i) Can act as vector/can self-replicate to form

multiple copies/ have selectable markers/
 small in size will facilitate insertion / presence
of ‘Ori’
E. coli, Agrobacterium tumefaciens,
Salmonella typhi, Bacteria , any other correct
example (any two)
(ii) ‘Ori’ – this is a sequence from where
replication starts / any piece of DNA when
linked to this sequence can be made to
replicate with in the host cells/controls copy
number of linked DNA.
§ Selectable marker helps in identifying and
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eliminating non-transformants, and

selectively permitting the growth of
transformants during recombinant DNA
technology.
(iii) Restriction endonuclease identifies a specific
palindromic sequence of DNA and cut the
DNA at the specific sites in both the host as
well in desired/foreign DNA, thereby creates
“sticky ends” facilitating ligation to form a
recombinant DNA

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 www.cbse.page

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◎ 2023 March
¥ 57/1 All Sets
š 2023 PYQ 44 ¥ 57/1, Set 1
Given below are two columns. In Column I is the
list of four enzymes and in Column II is the list of
functions of the given enzymes. Which one of the
following options shows the enzymes matched
with their respective functions correctly ?

Column I Column II
(Enzyme) (Function)
P. DNA Ligase i. Removes nucleotides
from ends of DNA
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Q. Restriction exonuclease ii. Extends primer on a

DNA template
R. Taq polymerase iii. Joins the DNA
fragments
S. Restriction iv. Cuts DNA at a specific
endonuclease position

(a) P-i, Q-ii, R-iv,S-iii (c) P-i, Q-iv, R-iii, S-ii

(b) P-iv, Q-iii, R-ii, S-i (d) P-iii, Q-i, R-ii, S-iv

Answer A 1 Marks
(d) P-iii, Q-i, R-ii, S-iv

š 2023 PYQ 45 ¥ 57/1, Set 1

The organism used in construction of the first
artificial recombinant DNA by Cohen and Boyer in
1972 was :
(a) E. coli
(b) Salmonella typhimurium
(c) Agrobacterium tumefaciens
(d) Bacillus thuringiensis
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Answer A 1 Marks

(b) Salmonella typhimurium

š 2023 PYQ 46 ¥ 57/1, Set 1

(i) Identify and name the structures ’A’ and ’B’

marked in the image given below:

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(ii) State their importance in various

biotechnology experiments.
OR
(b) Explain the process by which a bacterial cell
can be made ’competent’ to take up foreign
DNA from its surroundings, using divalent
cations and temperature treatment.

Answer A 2 Marks
(i) ‘A; Circular DNA/Plasmid‘B’ Bacteriophage
(ii) (Plasmid)-Can carry foreign gene into the host
cell/acts as cloning vector/has selectable
marker/ independent of the control of
chromosomal DNA/ high copy number
(Bacteriophage) - Cloning vector have the ability
to replicate in bacterial cells / independent of the
control of chromosomal DNA / high copy number
per cell.
OR
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(b) Treating bacteria with specific concentration

of calcium (ions)which increases the
efficiency with which DNA enters the bacteria
through pores in its cell wall ,recombinant
DNA can then be forced into such cells by
incubating the cells with recombinant DNA on
ice, followed by placing them briefly at 420C
(heat shock), then putting them back on ice.
š 2023 PYQ 47 ¥ 57/1, Set 1
With the help of a schematic diagram only, show
in three steps, the formation of recombinant DNA
by the action of restriction endonuclease EcoRI
and DNA ligase.

Answer A 3 Marks

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š 2023 PYQ 48 ¥ 57/1, Set 2
Given below are the steps carried out to construct
a recombinant DNA. Which one of the following
gives the correct sequence of these steps?

(i) Isolation of genetic material

(ii) Insertion of recombinant DNA in the host cell
/ organism
(iii) Obtaining the foreign gene product
(iv) Amplification of gene of interest
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(v) Downstream processing

(a) (i)→ (iii)→ (iv)→ (ii)→ (v)

(b) (i)→ (iv)→ (ii) →(iii) →(v)
(c) (ii)→ (i) →(iii) →(iv) →(v)
(d) (ii) →(iv)→ (v)→ (iii)→ (i)

Answer A 1 Marks

(b) (i)→ (iv)→ (ii) →(iii) →(v)

š 2023 PYQ 49 ¥ 57/1, Set 2

(a) Vectors are DNA molecules that can carry a

foreign DNA segment into the host cell.
(i) Write the significance of ’ori’ in this vector
(ii) Give one example each of vectors used for
cloning genes in plants and animals.
OR
(b) Write how can an alien DNA be introduced
into
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(i) an animal cell

(ii) a plant cell.

Answer A 2 Marks

(a) (i) ‘ori’ – a sequence from where replication

starts and any piece of DNA when linked to
this sequence can be made to replicate within
the host cells, this sequences is also
responsible for controlling the copy number
of the linked DNA
(ii) Plants – Agrobacterium tumefaciens
Animals – Retrovirus
OR
(b) (i) Micro injection, Recombinant DNA is
directly injected in the nucleus of an animal
cell
or
Retrovirus, animal cells are infected with
disarmed retrovirus
(ii) Biolistics or Genegun, Plants cell are
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bombarded with high velocity micro particles

of gold or tungsten coated with DNA (rDNA)
or
Agrobacterium tumefaciens, delivering gene
by disarmed pathogen.

š 2023 PYQ 50 ¥ 57/1, Set 3

Which of the following samples of DNA in the
table given below will give the desired result
during polymerase chain reaction?
 Temperature used Enzyme used for
Sample
for Denaturation extension
(a) I High temp. / 90°C Heat stable
(b) II Low temp. / 50°C Heat stable
(c) III Low temp. / 50°C Heat resistant
(d) IV High temp. / 90°C Heat unstable

Answer A 1 Marks

(a) I High temperature / 90°C Heat stable

š 2023 PYQ 51 ¥ 57/1, Set 3

www.cbse.page

Assertion (A) : In order to cut the DNA with a

restriction enzyme, it needs to be released from
the membrane which encloses it.

Reason (R) : A plant cell was treated with

chitinase to achieve this.

(a) Both Assertion (A) and Reason (R) are true and
Reason (R) is the correct explanation of the
Assertion (A).
(b) Both Assertion (A) and Reason (R) are true,
 but Reason (R) is not the correct explanation
of the Assertion (A).
(c) Assertion (A) is true and Reason (R) is false.
(d) Assertion (A) is false and Reason (R) is true.

Answer A 1 Marks

(c) Assertion (A) is true, but Reason (R) is false.

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 www.cbse.page

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◎ 2023 March
¥ 57(B)
š 2023 PYQ 52 ¥ 57(B), Set 1
The correct method of introducing alien DNA into
the appropriate host is :
(a) Microinjection - animal cell
(b) Incubating cells followed - nucleus of an animal
by temperature shocks cell/plant cell
(c) Biolistics - bacteria
(d) ‘Disarmed pathogen’ - plants
vectors

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Answer A 1 Marks

(a) Microinjection – Animal cell.

OR
(d) ‘Disarmed pathogen’ vectors – plants.

š 2023 PYQ 53 ¥ 57(B), Set 1

What trait is coded by the piece of DNA which is
introduced in E. coli, a host bacterium, as
compared to normal cells in transformation as
selectable markers ?
 Answer A 2 Marks

It in encodes for protein that provides antibiotic

resistance / It encodes for β galactosidase that
gives blue colour E.coli colonies in the presence of
chromogenic substrate, normal cell do not have
this trait.

š 2023 PYQ 54 ¥ 57(B), Set 1

Name the main enzyme involved in replication of
DNA in E. coli. List the two characteristics of this
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enzyme. What would happen if the enzyme makes

mistakes during replication ?

Answer A 3 Marks

§ DNA dependent DNA Polymerase/ DNA

Polymerase
§ Enzymes is fast, highly efficient, high degree of
accuracy, polymerise only in 5’ → 3’direction,
uses DNA template for replication, cannot
initiate the process of replication on its own.
§ Would result in mutations

š 2023 PYQ 55 ¥ 57(B), Set 1

Explain the process of isolation of DNA from a
plant cell, for recombinant DNA technology.

Answer A 3 Marks

Cell treated with cellulase to break the cell wall,

DNA along with other macromolecules like
RNA/proteins/polysaccharides/lipids released,
RNA removed by ribonuclease, proteins removed
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by protease, DNA precipitates out/ isolated, by

addition of chilled ethanol.
 www.cbse.page

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◎ 57/5 All Sets

¥ 2022 May Term 2
š 2022 PYQ 56 ¥ 57/5, Set 1
A cell free method of amplifying DNA first
developed in the mid 1980’s revolutionized the
field of biotechnology. Name the method and
explain the basic steps of the technique involved.

Answer A 3 Marks

§ Polymerase Chain Reaction / PCR

§ Denaturation by heating /DNA strands are
separated by heating. www.cbse.page

Annealing of two primers to complementary

region of DNA / Joining of primer to
complementary region of DNA

Extension of primers, using thermostable DNA

Polymerase or Taq Polymerase.

(The process is repeated many

times/amplification)
OR
 www.cbse.page

Polymerase Chain Reaction / PCR

š 2022 PYQ 57 ¥ 57/5, Set 1

Case Based Question

Cloning of genes, play a very significant role in
genetic engineering, helping the transfer of
desirable foreign genes into different hosts. The
scientists, to make this process easier and effective
are creating engineered vectors in such a way that
they help easy linking of foreign DNA and
selection of recombinants from non
recombinants. ‘pBR322’ is one such engineered
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vectors developed by scientists. A diagram of an

engineered vector pBR322 is given below :
 www.cbse.page

(i) Name the host for this cloning vector.

(ii) Identify ’Rop’ and ’Ori’ in the diagram from
‘U’, ‘V’, ‘W’, ‘X’, ‘Y’ and ‘Z’. Write their
functions.
(iii) Draw the fragments that will be formed by the
action of ’Z’ (marked in the diagram) on the
specific site of the DNA segment given below :
5’ - - - GTACGAATTCCTGA - - - 3’
3’ - - - CATGCTTAAGGACT - - - 5’
 Answer A 5 Marks

(i) E.coli / Escherichia coli

(ii) rop —‘W’, — code for the proteins involved in
the replication of the plasmid.

– ori —‘U’, — this is a sequence from where

replication starts / control the copy number of
the linked DNA
(iii) 5’—GTACG 3 ’ 5’ AATTCCTGA—3’
3’—CATGCTTAA 5’ 3’ GGACT—5’
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š 2022 PYQ 58 ¥ 57/5, Set 3

Non viral and non vector methods are sometimes
used to transfer genes or alien DNA into a plant
cell. Explain one such method used in genetic
engineering.

Answer A 3 Marks

§ Biolistics / Gene gun

§ Microparticles of gold or tungsten coated with
DNA, bombarded with high velocity into plant
cell

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 www.cbse.page

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◎ 57/4 All Sets

¥ 2022 May Term 2
š 2022 PYQ 59 ¥ 57/4, Set 1
Causative agents of HIV−AIDS and COVID−19
belong to the same group of viruses. To diagnose
and amplify the genetic material for further study
of COVID−19 virus, ‘RT−PCR’ test is carried out.
(a) What does ‘RT−PCR’ stand for ?
(b) Explain the various steps of PCR technique.

Answer A 2 Marks

(a) Real Time−Polymerase Chain Reaction /

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Reverse Transcriptase−Polymerase Chain

Reaction
Note : One mark is to be awarded for
attempting this question
(b) § Denaturation by heating /DNA strands are
separated by heating, Annealing of two
primers to complementary region of
DNA/ Joining of primer to complementary
region of DNA, Extension of primers, using
thermostable DNA Polymerase or Taq
Polymerase
(The process is repeated many
times/amplification)
OR

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š 2022 PYQ 60 ¥ 57/4, Set 1
Gene of interest / alien gene is introduced by a
cloning vector into a host cell to bring about a
desired phenotypic expression in a host cell. The
cloning vectors used are plasmid and
bacteriophages.

Biotechnologists in their labs, for desired results

engineered specialised cloning vectors. One such
vector is pBR322. Study the diagram carefully and
answer the questions that follow. www.cbse.page

(i) What do ‘EcoR I’, ’BamH I’ and ’Hind III’

 represent ? State their functions.
(ii) Identify the gene you would select for the role
of a selectable marker in pBR322. Explain why.

Answer A 5 Marks

(i) § All are restriction endonucleases

§ act as a molecular scissors / cut at a
specific site within DNA
R R
(ii) amp /tet , help in identification and selection
of transformants from non−transformants /
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identification of recombinant from non

recombinant
(iii) Have the ability to replicate within bacterial
cells independent of the control of
chromosomal DNA / Autonomously
replicating / bacteriophages and some
bacteria have high copy number per cell , can
replicate the desirable gene into large number
of copies, presence of selectable marker,
presence of cloning sites, presence of ori.
 OR
(iii) It is the sequence where replication begins / It
controls copy number of vector
(iv) No, identification and selection of
transformants from non−transformants /
identification of recombinant from non
recombinant would not be possible

š 2022 PYQ 61 ¥ 57/4, Set 3

Only with the help of a labelled diagram, show the
steps of formation of recombinant DNA by the
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action of restriction endonuclease enzyme EcoR I.

Answer A 3 Marks

Diagram in next page.

www.cbse.page
 www.cbse.page

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◎ 57/3 All Sets

¥ 2022 May Term 2
š 2022 PYQ 62 ¥ 57/3, Set 1

(a) Given below is the stepwise schematic

representation of the process of
electrophoresis.
Identify the ’alphabets’ representing
(i) Anode end
(ii) smallest / lightest DNA strand in the matrix
(iii) Agarose gel

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(b) What is elution? State the importance of

elution in this process.
 Answer A 3 Marks

(a) (i) S (ii) R (iii) T

(b) § Process of cutting of separated bands of
DNA, and extracting from the agarose gel.
§ Purified DNA is used in rDNA technology /
genetic experiments.

š 2022 PYQ 63 ¥ 57/3, Set 1

Case Based Question

Read the paragraph given below and answer the
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questions that follow:

Enzyme Taq polymerase, is extracted from a

eubacterial microorganism Thermus aquaticus
from Yellowstone National Park in Montana, USA
and isolated by Chien et al. (1976). Taq
polymerase successfully replaced the DNA
polymerase from E.coli that was being used in PCR
earlier and this shift revolutionised the PCR
technique.
 (i) Taq polymerase after its discovery replaced
E.coli DNA polymerase in PCR technique.
Explain giving reasons why was the need felt
for the change?
(ii) What is a primer and its importance in PCR?
(iii) Write the importance of PCR as a diagnostic
tool.

Answer A 5 Marks

(i) § The E.coli DNA polymerase cannot carry

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out PCR at high temperature (as it

becomes inactive).
§ Whereas Taq polymerase being
thermostable remains active even at high
temperatures.
(ii) § Primers are small chemically synthesised
oligonucleotides that are complementary
to the regions of genomic DNA strand
§ Primers help in extension of
complementary DNA strand
(iii) Early detection of diseases like cancer / AIDS /
genetic disorder, by amplification of desired
genes (when very low concentration of
bacteria or virus before setting of the disease
symptoms).

š 2022 PYQ 64 ¥ 57/3, Set 2

Restriction endonucleases are used in genetic
engineering to form recombinant DNA. Explain
only with the help of a flow chart the steps carried
in the formation of a recombinant DNA. www.cbse.page

Answer A 3 Marks

Restriction endonuclease cuts both DNA (vector

and foreign DNA) at the same site (a little away
from the centre of palindrome sites)
↓
Leaves single stranded portion at the ends of each
DNA strand / formation of sticky ends on each
DNA strand
↓
DNA fragments join at sticky ends by DNA ligase
to form rDNA.
OR

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OR
www.cbse.page
 www.cbse.page

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◎ 57/2 All Sets

¥ 2022 May Term 2
š 2022 PYQ 65 ¥ 57/2, Set 1
With the advent of sophisticated techniques of
genetic engineering, we can now readily purify
and isolate DNA.

Name and explain the different steps involved in

the separation and isolation of DNA fragments
once cut by restriction endonucleases.

Answer A 3 Marks

§ Gel electrophoresis www.cbse.page

§ Negatively charged DNA fragments (produced

by restriction endonuclease) move towards
anode through agarose gel, smaller fragments
move further, separated fragments are stained
with ethidium bromide, followed by exposure
to UV radiation, extraction of DNA bands by
elution.
š 2022 PYQ 66 ¥ 57/2, Set 1

Case Based Question

Development of recombinant DNA technology has opened gates to many
breakthroughs in the fields of medicine and agriculture. This has enabled
scientists to isolate, sequence and manipulate individual genes obtained
from diverse living or dead cells.

Given below is a diagram showing the basic steps involved in genetically

modifying an organism.

Study the given diagram and answer the questions that follow :
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(i) Are two different types of restriction endonucleases used, one to cut
the vector DNA and another to cut the desired DNA to be cloned?
Support your answer, giving reason.
(ii) Which enzyme is used at step (X) to integrate the foreign DNA with
the vector DNA ?
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(iii) What is the term used for step (Y) showing multiple copies of the
foreign DNA being formed in transformed E. coli ?
(iv) Draw a diagram of E. coli cloning vector pBR322 to show the following
(I) Any one restriction endonuclease site in tetracycline resistance
gene
(II) Any one restriction endonuclease site in ampicillin resistance
gene
(III) ‘ori’ site
(v) What does rop code for in plasmid pBR322?

Answer A 5 Marks

(i) No, Cut with same restriction endonuclease to obtain complementary

sticky ends / to obtain DNA fragments with same kind of sticky ends
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 (which can be joined together end to end)
(ii) DNA ligase
(iii) Cloning / Host Cloning / Gene Cloning
(iv) .

I. BamH1 or SalI
II. Pvul or Pst1
III. Ori
(any two correct labellings)

(v) Codes for the proteins involved in replication of the plasmid

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š 2022 PYQ 67 ¥ 57/2, Set 2
"Large scale production of DNA recombinant
requires the use of bioreactors."
(a) Draw a labelled diagram of a simple
stirred-tank bioreactor.
(b) State why a simple-stirred tank bioreactor
generally has a curved base.

Answer A 3 Marks

(a) (any four labellings)

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(b) It has a curved base to facilitate the mixing of
the reactor contents

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 www.cbse.page

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◎ 57/1 All Sets

¥ 2022 May Term 2
š 2022 PYQ 68 ¥ 57/1, Set 1
Name two naturally occurring sources, one that
transfers pathogenic genes into a plant cells and
the other into an animal cell respectively, for their
benefit. Write how have these naturally occurring
sources been used for the benefit of human race
by the biotechnologists.

Answer A 3 Marks

§ Agrobacterium tumefaciens−(plants www.cbse.page

pathogen), The disarmed Ti Plasmid is used as

a vector to introduce the gene of interest in the
variety of plants.
§ Retrovirus−(animals), Disarmed Retroviruses
are used to transfer genes of interest in to
mammalian host cells.
š 2022 PYQ 69 ¥ 57/1, Set 1

(i) State the role of a selectable marker in r−DNA

technology.
(ii) Name one such selectable marker which is
considered to be useful for E.coli.
(iii) Give one reason why is it considered to be a
useful marker.
OR
What are plasmids ? How are they different from
cloning vectors? Give one example each for a viral
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and a bacterial cloning vector.

Answer A 3 Marks

(i) Helps in identifying non−transformants from

transformants / Recombinants from non
Recombinants
(ii) Genes encoding resistance to antibiotics such
as ampicillin / tetracycline/ kanamycin /
R R
chloramphenicol / amp / tet
(iii) (The normal E. coli cells do not carry
resistance against any of thesebantibiotics.) It
helps to identify and mnselect transformants /
identification of recombinants.
OR
§ Plasmids are extra chromosomal
self−replicating (double stranded) circular
DNA molecules (generally found in bacterial
cell)
§ Plasmid is circular extra chromosomal DNA of
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bacterial cells whereas cloning vector is a

vehicle that carries foreign DNA into another
cell.
§ Bacteriophage, pBR322
š 2022 PYQ 70 ¥ 57/1, Set 1

Case Based Question

To save the crop plant from the attack of various
insect pests the biotechnologists have developed
many pest resistant plants. One such example is
Bt corn plant. In this plant ‘cry’ genes were
introduced which produces cryproteins in the
plant that has toxic effect on the pest (corn borer).
Thus saves the corn plant from the attack of the
corn borer. An experimental field study was
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conducted by the scientists to see the efficacy of

the Bt corn plant against the attack of corn borers.
Three different species of corn borers namely ‘A’,
‘B’, ‘C’ were collected and were independently fed
on non Bt corn plants and Bt corn plants
separately for the same period. The extent of the
damage caused to the leaf area of the plant was
observed and noted down. With the help of the
observations and data collected the following bar
graph was plotted.
Study the graph and answer the questions that
follow.

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(i) Identify the species of the corn borer that was

most successfully controlled by Bt corn plant.
Give appropriate reason for your inference.
(ii) Identify the species of the corn borers which
shows least impact of toxin produced by Bt
genes.
(iii) What would be your advise as a Scientist, to
the farmers for growing this particular Bt corn
variety in the area which is infested by
 species-’B’ of corn borers?
(iv) Name one Bt gene that encodes protein in
corn plants to control corn borers.
OR
A gene was identified in a fungus by a research
worker in a lab which was considered to be of a
great importance in the field of agriculture. As a
student of biotechnology, write the steps you
would suggest to (i) Isolate this gene of interest
from the fungus and (ii) amplify this gene for
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further experimentation and research.

Answer A 5 Marks

(i) § Species A
§ The leaf area damaged by species - A in
Bt-corn is the least.
(ii) Species-B
(iii) Not to grow Bt variety as seeds are expensive
and of not much benefit (productivity wise) /
advise to grow Bt corn with its proper
 justification
(iv) Cry IAb. (No marks if only cry gene is written)
OR
(i) § (Isolation of genetic material) Fungal cell
treated with chitinase, RNA to be removed
by treating with RNAase protein removed
by treating with protease, and theb mi
koiaddition of chilled ethanol.
§ Cutting of DNA at specific location by
restriction enzymes.
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§ Fragments are separated by gel

electrophoresis
(ii) Multiple copies of separated genes of interest
is synthesized by following steps of the
method given below: PCR (polymerase chain
reaction) Denaturation, Annealing, Extension
( followed by amplification)
OR
(ii) Polymerase chain reaction/PCR
 www.cbse.page

OR
(ii) Multiple copies of separated genes of interest
are synthesized by following the given below
method: rDNA technology, same restriction
enzyme cutting both foreign DNA and vector
DNA at specific point, ligases join foreign
DNAto Plasmid, transformation (cell divides
and helps in multiplication of genes)
 OR
(ii) rDNA technology

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š 2022 PYQ 71 ¥ 57/1, Set 3
Name any three techniques used for introducing
an alien DNA into a host cell and mention how ?

Answer A 3 Marks

§ Microinjectionre−combinant DNA is directly

injected into the nucleus of an animal cell.
§ Biolistics or gene gun−Host cells are
bombarded with high velocity micro−particles
of gold or tungsten coated with DNA. www.cbse.page

§ Disarmed pathogen vectors−transfers the

recombinant DNA into the host cells when
allowed to infect
§ Heat shock method−recombinant DNA is
forced into competent bacterial cells by
incubating the cells with recombinant DNA on
ice, followed by placing them briefly at 42
degree Celsius (heat shock) and then putting
them back on ice.
 www.cbse.page

Competency Based Questions

Answers are given after all the questions end.
š CBQs 1 [1 Marks]

Nihal said that bacteria are never used as a host to

clone recombinant DNA for antibiotic production.

Is his statement correct and why?

(a) Yes, because antibiotics kill host bacterial

cells.
(b) No, because antibiotics only kill cells other
than bacterial cells.
(c) No, because the foreign DNA or the host
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bacterial cell is resistant to the antibiotic being

produced.
(d) Yes, because host bacterial cells do not have
the machinery to allow the growth of an
antibiotic obtained from other microbes.

š CBQs 2 [5 Marks]

A researcher used a vector X to insert a foreign

gene to create a recombinant vector. The image of
vector X is shown below.
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It has sites for two restriction enzymes - SacI and

EcoRI. The foreign gene can be cut using either of
these two enzymes. The vector also has a green
fluorescent protein (gfp) gene that can be used as
a selectable marker, and two genes -
chloramphenicol resistance (CmR) and neomycin
resistance (NeoR) that provide antibiotic
resistance. Chloramphenicol and neomycin are
two different antibiotics.
(a) What is/are the possible end product(s) that
will be obtained post-ligation if the researcher
uses the following enzyme to insert the foreign
gene :
(i) SacI
(ii) EcoRI
(b) Based on (a), which enzyme will be better to
use to ensure that the foreign gene has been
inserted in the vector? Why?
(c) If the well of an agarose gel is filled with a
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solution of the intact vector and the foreign

gene, what will the DNA band closer to the
well contain? Why?
š CBQs 3 [5 Marks]

The large-scale production of an organism is

generally done in a bio-processor unit. Given
below is the growth curve of a bacteria that is
being used for the production of a recombinant
molecule. Maintaining sterile conditions is of
utmost importance in a bio-processor unit.

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(a) In which phase are the cells likely to be

producing a larger concentration of the
recombinant molecule? Why?
(b) In cases where the culture in the bio-processor
unit reaches the death phase, identify ONE
 strategy that can help revive the
bio-processing to restart production of the
recombinant molecule.
(c) What does a sterile condition mean
(d) State ONE reason why the bacteria that are
producing the recombinant molecule are not
harmed during the process of sterilisation.

š CBQs 4 [3 Marks]

Bacterial cells offer certain advantages over plant

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or animal cells that make them an easy choice for

the production of many recombinant molecules.
State THREE such advantages

š CBQs 5 [2 Marks]

Give TWO reasons why it is important to introduce

the gene/s of interest in a vector and then into the
host cell or insert it directly into the host
chromosomal genome.
 š CBQs 6 [2 Marks]

pBR322 was a plasmid that was constructed

artificially using genetic material from three
sources:
(i) the tetracycline resistance gene of pSC101
(ii) the ampicillin resistance gene of RSF 2124
(iii) the replication elements of pMB1, a close
relative of the ColE1 plasmid.

Describe the TWO enzymatic steps that would

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have occurred in the construction of pBR322.

š CBQs 7 [2 Marks]

In the process of DNA replication, RNA primers

are used to initiate replication where a free
nucleotide can start forming a bond with the RNA
primer as per the leading strand base sequence.
Later, this RNA primer needs to be removed.

What type of a nuclease can help with this activity?

Why?
š CBQs 8 [5 Marks]

The basis of rDNA technology is to alter the

genetic material of an organism to obtain
enhanced and desired characteristics in an
organism.
(a) Preferably, the gene of interest and the vector
are cut with the same restriction enzyme. Is
this statement true? Give a reason to support
your answer.
(b) What is/are ALL the possible outcomes after
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the gene of interest and the vectors are ligated?

(c) If a vector contains an ampicillin resistance
gene as the selectable marker, state TWO
situations in which the host cell will grow in a
medium that contains ampicillin.
š CBQs 9 [3 Marks]

State whether each of these statements given

below is/are true or false. Justify your answer.
(a) Plasmids with a single restriction site are
preferred over those with multiple sites for the
same enzyme during the cloning process.
(b) The tumour-inducing (Ti) plasmid can be
extracted from Agrobacterium tumifaciens
cells and used as it is for cloning a foreign
gene. www.cbse.page
š CBQs 10 [5 Marks]

Vectors containing the foreign DNA have to be

forced into host cells that are made competent to
do so. A common method is to first treat host cells
with calcium chloride and then incubate these
cells on ice. This is followed by briefly placing
them at 42 °C and then putting them back on ice.
This enables the host cells to take up recombinant
DNA and is called the heat shock treatment.

(a) Explain why DNA vectors CANNOT pass www.cbse.page

through the cell membrane like other

molecules such as oxygen.
(b) Calcium from a CaCl2 solution binds to DNA
making it easier for them to enter a cell. Why?
(c) Why does the heat shock treatment make the
membrane porous allowing for easy uptake of
DNA?
š CBQs 11 [5 Marks]

Polymerase chain reaction (PCR) is an in-vitro

technique used to amplify nucleic acid sequences.
The conditions and duration of each step in PCR
are as follows:

- Step 1 at 94 °C for 2 min

- Step 2 at 50-65 °C for 30 seconds

- Step 3 at 72 °C for 5 min

(a) Give TWO reasons why amplification using

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PCR can be better than amplification in-vivo

using plasmids.
(b) At which step does the denaturation of DNA
take place? How does this occur?
(c) What would be the result of the PCR reaction if
step 2 does not occur?
(d) At what step would PCR be important in rDNA
technology?
š CBQs 12 [3 Marks]

Insulin is commonly prepared in bio-processing

units for patients suffering from
insulin-dependent diabetes.

Explain THREE steps that would be a part of the

downstream processing for insulin.

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š CBQs 13 [3 Marks]

Given below is a diagram of a bio-reactor with

some of its parts labelled P and Q

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(a) Which type of organisms can MOST likely be

used if part P is not made a part of the
 bio-reactor? Why?
(b) Identify the name and purpose of part Q.
(c) How does the thermal jacket help in the
process?

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 Answers
š CBQs Answer 1
D. Yes, because host bacterial cells do not have the
machinery to allow the growth of an antibiotic
obtained from other microbes.

š CBQs Answer 2
(a)
(i) § self-ligated vectors/vectors without the
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foreign gene inserted

§ vectors with the foreign gene ligated at any
of the two positions
§ self-ligated vectors without the foreign
gene and the neoR gene
§ self-ligated vectors with the foreign gene
but without the neoR gene
(ii) § self-ligated vectors/vectors without the
foreign gene inserted
 § vectors with the foreign gene inserted
inside the CmR gene.
(You can use drawing two illustrate your
answer)
(b) § EcoRI is a better enzyme to use.
§ Use of EcoRI will ensure the foreign gene
insertion because apart from the presence
of gfp, it will also be susceptible to
chloramphenicol. So only colonies that do
not grow on the
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chloramphenicol-containing medium will

have the foreign gene inserted.
(c) § intact vector
§ DNA fragments in an agarose gel move
depending on their size where larger
fragments stay close to the well while
smaller fragments move further away.
š CBQs Answer 3
(a) § exponential growth phase
§ that is the phase where biomass is highest
and so each cell produces the
recombinant molecule causing its overall
concentration to be the highest in the unit
(b) § addition of more microbes in the growth
phase
§ adding fresh medium while removing the
used-up medium www.cbse.page

(c) A sterile condition refers to the absence of

contaminating organisms in a system
(d) § bacterial culture of interest is added after
the sterilisation process
§ if the bacteria of interest is
thermophilic/die at higher temperature
than that used for sterilisation
š CBQs Answer 4
§ Bacterial cells replicate much faster than plant
or animal cells.
§ Bacterial cells naturally possess
extrachromosomal DNA which can act as
carriers for the recombinant DNA.
§ Absence of the nuclear membrane in bacterial
cells makes it easy to introduce the
recombinant plasmid to the replication,
transcription and translation machinery of the
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cell.

š CBQs Answer 5
§ An alien piece of DNA in the cytoplasm is
likely to get degraded.
§ A piece of DNA will not get replicated without
the origin of replication and so will not get
inherited.
š CBQs Answer 6
§ The DNA sequences coding for the antibiotic
resistance genes and the replication elements
would have been cut from the original plasmid
using appropriate restriction enzymes.
§ The fragments created after restriction
digestion would need to be ligated using DNA
ligase to construct the vector.

š CBQs Answer 7 www.cbse.page

§ exonuclease
§ Since the nucleotides from the end of the DNA
strand need to be removed exonucleases can
help with the activity.

š CBQs Answer 8
(a) § True
§ If the gene of interest and vector are cut
with the same restriction enzyme they will
 produce the same sticky ends that are
complementary to each other, making
ligation easier.
(b) § self-ligated vector/s
§ two of more genes of interest self-ligate
§ gene of interest and vector ligate
(c) § If the gene of interest ligates into the
vector and gets transformed into the host
cell.
§ If the vector self-ligates and gets
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transformed into the host cell.

š CBQs Answer 9
(a) § True
§ Plasmids with a single restriction site get
cut at only one site increasing the
possibility of obtaining a cloned vector
rather than those with multiple cleaving
sites for the same enzyme.
(b) § False
 § Plasmids extracted from the bacteria
cannot be used as it is as the pathogenic
genes need to be removed before it can be
used as a vector.

š CBQs Answer 10
(a) § The cell membrane is an amphipathic
structure whose outer ends are
hydrophobic or non-polar in nature.
§ Oxygen being a non-polar molecule can
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enter the cell easily but DNA is highly

polar / hydrophilic in nature which is
repelled by the cell membrane.
(b) § DNA is a negatively charged molecule and
this makes it highly polar in nature.
§ Calcium are divalent cations which bind
to DNA making it non-polar and so easier
to cross the cell membrane.
(c) An increase in temperature results in greater
kinetic energy of molecules making the
 membrane more fluid / porous.

š CBQs Answer 11
(a) § PCR is faster than the generation time of
many microbes.
§ An origin of replication is not required for
PCR as is required in plasmids.
(b) § Step 1
§ Heat causes denaturation of DNA.
(c) No DNA would be amplified OR the reaction
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would stop.
(d) PCR would be an important step just before
the process of ligation, done before
transformation into the required host.

š CBQs Answer 12
§ The first step would be extraction of the
protein from the cells in which it is produced.
§ The second step would be to purify only
insulin from the other cell contents that would
 get mixed in the process of extraction.
§ The third step would be to store insulin at low
temperatures to prevent denaturation of the
hormone.

š CBQs Answer 13
(a) Anaerobic organisms
Reason - since the aerator ensures supply of
oxygen for aerobic organisms to respire and
function, anaerobic organisms will not need
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this to carry out life processes.

(b) Q - stirrer/agitator
Purpose - The stirrer facilitates even mixing
and oxygen availability throughout the
bio-reactor.
(c) to maintain temperature throughout the
process
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