PRE- BOARD EXAMINATION (2022-23)

CLASS - XII
SUBJECT – BIOLOGY
TIME : 3 HRS MM- 70
General Instructions:
(i)All questions are compulsory.
(ii)The question paper has five sections and 33 questions. All questions are compulsory.
(iii)Section–A has 16 questions of 1 mark each; Section–B has 5 questions of 2 marks each; Section– C
has 7 questions of 3 marks each; Section– D has 2 case-based questions of 4 marks each; and Section–E
has 3 questions of 5 marks each.
(iv)There is no overall choice. However, internal choices have been provided in some questions. A
student has to attempt only one of the alternatives in such questions.
Wherever necessary, neat and properly labeled diagrams should be drawn.
SECTION - A
1 Which type of the following pyramid is never inverted?
(a) Pyramid of energy
(b) Pyramid of biomass
(c) Pyramid of number
(d) Pyramid of dry biomass
2 Identify the structures marked A to D in the given figure.

a Exine intine generative cell vegetative cell

b Exine intine vegetative cell generative cell
c Exine vegetative cell intine generative cell
d Intine generative cell vegetative cell exine
3 The technique called Gamete Intra Fallopian Transfer (GIFT) is recommended for those
females
(a)who cannot produce an ovum
(b)who cannot retain the foetus inside uterus
(c)who cannot provide suitable environment for fertilisation
(d) all of these
4 Spot the odd one out from the following structures with reference to the male reproductive
system:
(a)Rete testis (b)Epididymis
(c)Vasa efferentia (d)Isthmus
5 Competition is most fierce between which of the following:
SPECIES ENVIRONMENT
1 Unrelated species Same environment
2 Two or more closely related species Same environment
3 Two or more closely related species different environment
4 Unrelated species different environment
6 Mother and father of a person with ‘O’ blood group have ‘A’ and ‘B’ blood group,
respectively. What would be the genotype of both mother and father?
option Blood group of father Blood group of mother

a heterozygous for ‘B’ homozygous for ‘A’

b homozygous for ‘B’ heterozygous for ‘A’
c heterozygous for ‘B’ heterozygous for ‘A’
d homozygous for ‘B’ homozygous for ‘A’
7 Two genes ‘A’ and ‘B’ are linked. In a dihybrid cross involving these two genes, the F1
heterozygote is crossed with homozygous recessive parental type (aa bb). What would be
the ratio of offspring in the next generation?
a. 1 : 1 : 1: 1 b. 9 : 3 : 3 : 1
c. 3 : 1 d. 1 : 1
8 Write the results of the experiment A-D shown below:

1 mice lives mice dies mice dies mice lives

2 mice lives mice lives mice dies mice lives
3 mice lives mice dies mice dies mice dies
4 mice lives mice dies mice lives mice dies
9 By the statement ‘survival of the fittest’, Darwin meant that
(a)the strongest of all species survives (b)the most intelligent of the species
survives
(c)the cleverest of the species survives (d)the species most adaptable to changes
survives
10 Golden rice is a promising transgenic crop. When released for cultivation, it will help in
(a)High lysin content (b)Pest resistance
(c)High protien content (d)High vitamin A content
11 log S = log C + Z log A
In the given equation of species-area relationship, the value of regression coefficient for a
whole continent, would be
Range from Range upto
a 0.1 0.2
b 0.5 0.7
c 0.6 1.2
d 0.3 0.5
12 The site of production of ADA in the body is
(a) Erythrocytes (b) Lymphocytes
(c) Blood plasma (d) osteocytes
Directions: In the following questions, a statement of assertion is followed by a statement
of reason.
Mark the correct choice as:
(a)If both Assertion and Reason are true and Reason is the correct explanation of
Assertion.
(b)If both Assertion and Reason are true but Reason is not the correct explanation of
Assertion.
(c)If Assertion is true but Reason is false.
(d)If Reason is true but Assertion is false
13 Assertion : Autogamy is a transfer of pollen grains from an anther to the stigma of the
same flower on the same plant.
Reason : Xenogamy is pollination between two flowers on different plants.
14 Assertion : Mendel was successful in his hybridization.
Reason : Garden pea proved ideal experimental material.
15 Assertion: Restriction endonucleases are also called ‘molecular scissors’.
Reason: When fragments generated by restriction endonucleases are mixed, they join
together due to their sticky ends.
16

Assertion : Indo-Gangetic plains have high population density.

Reason: These have favourable climate and fertile soil
SECTION B
17 Draw the diagram of human sperm. Label any 2 parts and mention their functions
18 A bilobed, dithecous anther has 100 microspore mother cells per microsporangium. How
many male gametophytes this anther can produce?
19 Amniocentesis, the technique of sex determination given below is banned in our country.
Is this ban necessary? Comment.

20 Define and design a test-cross.

OR
If the sequence of the coding strand in a transcription unit is written as follows: 5′ -
ATGCATGCATGCATGCATGCATGCATGC-3′
Write down the sequence of mRNA.
21 White and dark coloured moths are shown below. State a reason for the increased
population of dark-colored moths coinciding with the loss of lichens, after
industrialization

SECTION C
22 After implantation interdigitation of maternal and foetal tissues takes place. Identify the
tissues involved and justify the role of structure formed.
23 Compare the two ecological pyramids of biomass given below and explain the situations
in which this is possible. Also construct an ideal pyramid of energy if 200,000 joules of
sunlight is available.
24 When a cross in made between tall plant with yellow seeds (TtYy) and tall plant with
green seed (Ttyy), what proportions of phenotype in the offspring could be expected to
be
(a)Tall and green. (b)Dwarf and green.
25 With respect to Meselson and Stahl’s Experiment, answer the following questions:
(a)Identify the method used to distinguish between heavy and light isotopes of nitrogen.
(b)With the help of diagrams, compare the results for the DNA isolated after 20 minutes
of experiment with the DNA which was isolated after 40 minutes.
OR
Explain Convergent and Divergent Evolution with examples.
26 Mention three Differences between Active and passive immunity with one example of
each.
27 If a double stranded DNA has 20 per cent of cytosine, calculate the percent of adenine in
the DNA.
28 The Evil Quartet explains the accelerated rate of species extinction world wide. Describe
any three of them with suitable examples
SECTION D
Q No. 29 and 30 are Case based questions. Each question has subparts with internal
choice in one subpart.
29 Following figure shows the source, mode of transmission of pathogen into the host

How does the transmission of each of the following diseases take place?
(a) Amoebiasis (b) Malaria (c) Ascariasis OR Ring worm (d) Pneumonia OR Fliariasis
30 Rajesh was doing gel electrophoresis to purify DNA fragments with the observations as
shown below

a)What is gel electrophoresis?

b)At which end he would have loaded the sample and where?
Analyse the reason for different positions M and N taken up by the DNA bands.
OR
Elaborate the steps that you would follow to visualize the DNA Bands.
 SECTION E
Draw the representation of genes involved in the lac operon –
(a)Identify the region where the repressor protein will attach normally.
(b)Under certain conditions repressor is unable to attach at this site. Explain.
(c)If repressor fails to attach to the said site what products will be formed by z, y
and a?
(d)Analyze why this kind of regulation is called negative regulation.
OR

Here, X axis is showing trait and Y axis is showing no. of individuals with
phenotype
(a)Identify A,B,C ,three different ways in which natural selection can affect the
frequency of a heritable trait in a population. Explain them.
(b)Write the Hardy Weinberg’s principle along with its equation.
32 Given below is a figure of a biogas plant.
(a)Identify A and justify its floating nature.
(b)Identify the products B and C and discuss their significance. (c)Mention any
four sites of production of methane.

OR
a)A patient who is suffering from myocardial infarction is given a clot buster as
part of his treatment. Mention the clot buster administered and its microbial
source.
b)A person recuperating from illness is advised to have curd regularly. Why?
A doctor prescribed morphine as a sedative and pain killer to your cousin who had
undergone surgery. Even after recovery, he craved for the prescribed medicine.
What do you conclude about his condition, had he continued with the same
medication? After appraising yourself, what measures will you suggest to him to
overcome this problem? Briefly explain any two.
33

a)(i) How are the two short peptide chains of insulin linked together ?
(ii)State the role of C peptide in human insulin.
(iii)Mention the chemical change that proinsulin undergoes, to be able to act as mature
insulin
b)What are the three advantages of recombinant insulin?
c)What are the three drawbacks of the insulin obtained from slaughtered cows and pigs?
d)Name the regions A, B, and C.
OR

(a)A gene was being ligated to the plasmid vector to prepare a recombinant DNA during
bacterial transformation. An exonuclease was added to the tube accidentally. How will it
affect the next step of the experiment?
(b)What are the four salient properties of a good cloning vector?