SBL100 MAJOR EXAMINATION

2023-24 SEMESTER II
ANSWER KEY:

1. Which of the following statements are true:

A. The DNA polymerase has an error rate of 1 in 105 that results in between 100-1000 errors
introduced everytime our cells divide.
B. The DNA polymerase does not introduce any errors during DNA replication and our cells faithfully
copy the DNA to pass onto daughter cells.
C. The DNA polymerase has an error rate of 1 in 108 that results in ~1 error introduced everytime
the cell divides.
D. The DNA polymerase introduces error only when replicating the ends of the chromosome
resulting in accumulation of chromosomal aberrations with successive replication.

2. Which kind of mutation can be transmitted from parent to progeny?

A. Point mutations, deletions and insertions in somatic cells

B. Chromosomal aberrations in somatic cells

C. Chromosomal aberrations in germ cells

D. Point mutations, deletions and insertions in epithelial cells

3. You have detected a point mutation in an individual. However, the individual does not display any
disease or altered phenotype. Your friend reasons that the following four could be the reason for the
absence of an associated disease or phenotype.

(i) The mutation may be synonymous mutation resulting in the replacement of an amino acid with a
structurally and biochemically similar amino acid

(ii) The mutation may fall within the intronic region of the gene.

(iii) The mutation is a non-sense mutation that results in a truncated protein.

(iv) The mutation is a transversion that can be easily reversed by demethylation of thymine to uracil

(v) The mutation is in one copy of the gene and the second good copy still produces the functional
gene product.

Which of the statements are CORRECT?

(A) (i) (ii) (v)

(B) (ii) (iii) (iv)

(C) (i) (iii) (iv)

(D) (ii) (iii) (v)

4. Match the immune cells with their attributes

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 Cell type Attribute
T cells 1. contain hemoglobin
B cells 2. involved in cytotoxic cell death
Neutrophils 3. blood coagulation
Platelets 4. antibody secretion
Red blood cells 5. phagocytosis

(A) T cells 2, B cells 4, Neutrophils 5, Platelets 3, Red blood cells 1

(B) T cells 5, B cells 4, Neutrophils 2, Platelets 3, Red blood cells 1

(C) T cells 2, B cells 5, Neutrophils 4, Platelets 3, Red blood cells 1

(D) T cells 4, B cells 2, Neutrophils 5, Platelets 3, Red blood cells 1

5. A mother has approached the court saying that person X is the father of her child. The court
observes that the mother has blood group O-ve while the child has a blood group of B+ve. Which of
these scenarios if TRUE for the person X will make him the suspected father?

(A) X is B-ve

(B) X is AB+ve

(C) X is O+ve

(D) X is A+ve

6. Match the following cell types with their attributes – zygote, embryonic stem cells, neuron

A. totipotent, pluripotent, unipotent

B. totipotent, totipotent, unipotent

C. pluripotent, pluripotent, unipotent

D. totipotent, pluripotent, multipotent

7. When challenged by an antigen, B cells producing antibody against that specific antigen increase in
numbers. This phenomenon is an example of:

A. clonal expansion

B. differentiation

C. epitope

D. regeneration

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8. Spemann and Mangold experiment that demonstrated the organizer cells could initiate a second
body axis when transplanted into an embryo. What event is initiated by the organizer? If you were to
cut out the organizer and put it into a petridish, what would you observe with the organizer?

A. Gastrulation, the organizer cells will move in the petri dish mimicking the movement during the
initiation of gastrulation.

B. Fertilization, the organizer cells will cease to move

C. Blatulation, the organizer cells will move in the petri dish mimicking the movement during the
initiation of gastrulation.

D. Zygote, the organizer cells will cease to move

9. In extrinsic apoptosis, the caspase activation is induced by signals “SENT” by a T lymphocyte that is
“RECEIVED” by the damaged cell. This type of signaling is an example of?

A. Paracrine signalling

B. Autocrine signalling

C. Endocrine signalling

D. Juxtacrine signalling

10. What happens to the apoptotic bodies that are shed by a damaged cell?

A. The apoptotic bodies self-destruct

B. The apoptotic bodies are cleared by macrophages

C. The apoptotic bodies are taken up by neighbouring cells

D. The apoptotic bodies enter the blood stream and get cleared in the kidney

11. Peyton Rous in his famous experiment with chicken sarcoma obtained a piece of chicken sarcoma
tissue and ground it with sand. He used the filtrate of the ground sarcoma and injected it into a
healthy chicken. What did he observe and what caused this phenomena?

A. The recipient chicken developed sarcoma and was attributed to a virus that was retained in the
filtrate.

B. The recipient chicken was healthy demonstrating that sarcoma required live cells and not filtrate

C. The recipient chicken was dead within minutes of injection because of toxins emanated by the
sarcoma

D. The recipient chicken was healthy due to immunity against the sarcoma developed by the
recipient chicken.

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12. You have discovered a potential gene linked to cancer. You have made the following observation:

(i) Both copies of the gene were observed to be mutated in patients

(ii) The gene codes for a protein that stimulates apoptosis in cells with DNA damage

(iii) The gene is expressed at low levels in cells but its expression increases when cells are exposed to
UV radiation.

Based on the above attributes your conclusion about the gene is?

A. Oncogene

B. Tumor suppressor

C. Inhibitor of apoptosis

D. Carcinogen

13. Below is a snapshot of GPCR signalling. Indicate which events correspond to : Signal initiation,
cascade, amplification and signal attenuation

A. Signal initiation (A), cascade (B), amplification (C) and signal attenuation (D)

B. Signal initiation (A), cascade (C), amplification (B) and signal attenuation (D)

C. Signal initiation (A), cascade (D), amplification (C) and signal attenuation (B)

D. Signal initiation (D), cascade (B), amplification (C) and signal attenuation (A)

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14. Till and McCulloch lethally irradiated mice to ablate all their blood cells. The mice could survive
only when transplanted with healthy marrow cells from a donor non-irradiated mice. What was the
cause of this?

A. The donor mouse bone marrow had stem cells that could produce all the blood cells in the
recipient mouse.

B. The donor mouse marrow could itself produce all the blood cells since bone marrow is the site for
blood cell production

C. The donor marrow was non-irradiated and hence the blood cells in it survived throughout the life
span of the recipient mice.

D. The donor marrow contained all the blood cells necessary for the survival of the irradiated mouse.

15. Protein kinase catalyses

a. the phosphorylation of effector protein.

b. the dephosphorylation of effector protein.
c. the activation of nucleotide exchange factor.
d. the activation of nucleotide dissociation factor.
16. Which of the following signaling events involves during insulin action?

a. Paracrine signalling
b. Endocrine signalling
c. Autocrine signalling
d. Juxtacrine signalling

17. Which of the following process regulate the programmed cell death?

a. Necrosis
b. Lysis
c. Apoptosis
d. Senescence

18. In the intrinsic pathway of apoptosis, mitochondria releases

a. Bid
b. Bax
c. cytochrome c
d. cytochrome b

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19. In receptor mediated endocytosis, ligand binds with specific receptor on cell surface
and internalized into endosomal compartment where low pH dissociate the ligand with
receptor. Which of the following receptor does not dissociate with ligand in endosome and
receptor-ligand complex recycles back to the cell surface?

a. LDL receptor
b. EGF receptor
c. Transferrin receptor
d. NGF receptor

20. Which one of the following adaptor molecule binds with cytoplasmic domain of plasma
membrane receptor?

a. AP1
b. AP2
c. AP3
d. AP4

21. Which of the following receptor used by the dengue virus to enter into macrophages?

a. LDL receptor
b. CD4 receptor
c. Mannose receptor
d. Transferrin receptor

22. Different pathogens enter into specific host cell by binding with specific cell surface
receptor via their own molecule. Which of the following interaction is correct between
pathogen protein with specific receptor?

a. Gp120 of HIV binds with CD4 Receptor on T cells.

b. Gp110 of HIV binds with CD8 Receptor on T cells.
c. Spike protein of SARs-CoV-2 binds with Mannose Receptor on macrophages.
d. Gp110 of Leishmania binds with Band3 protein on RBC.

23. Bacteria internalized by macrophages are degraded in which intracellular

compartment?

a. Early endosome and pH 6

b. Late endosome and pH 6
c. Lysosome and pH 4.5
d. Peroxisomes pH 5

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 24. In humoral immunity which kinds of cells are activated to produce antibody against
invading pathogen?

a. CD 4 cells
b. CD8 cells
c. NK cells
d. Mast cells

25. Which of the following statement is correct regarding Exergonic and endergonic reactions

a) Exergonic reactions are endothermic reactions which involves formation of bonds during the
formation of reaction intermediates
b) Exergonic reactions are exothermic reactions which involves breaking of bonds during the
formation of reaction intermediates
c) Endergonic reaction are catabolic reactions with negative ∆G
d) Endergonic reaction are anabolic reactions with positive ∆G

26.

1. What is the function of restriction enzymes in nature?

a. Repairing damaged DNA
b. Cutting foreign DNA for defense
c. Transcribing RNA
d. Synthesizing proteins

27.

1. Which of the following statements about the lac operon is true?

a. It is always active regardless of lactose concentration
b. It is an example of positive regulation
c. It consists of only one gene
d. It is found in eukaryotic cells

28.

1. What is the function of the operator in the lac operon?

a. It synthesizes lactose
b. It binds to the lac repressor
c. It codes for regulatory proteins
d. It initiates transcription

29.

1. Calculate the Standard Free Energy Change at 25 ᵒC given the Equilibrium constant of 1.3 x 104.
a) +23.4 kJ
b) - 3.22 x 10^4 kJ
c) -23.4 kJ

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 d) +23,400 kJ

30.

2. The reaction A + B ⇆ C is an exothermic reaction; if an equilibrium mixture of A, B, and C

is heated slowly, what would happen to the concentrations of each species?
a) All three concentrations decreases
b) All three concentrations decreases
c) A and B increases, C decreases
d) A and B decreases, C increases

31. What cellular organelle(s)/structure(s) could NOT be observed in animal cells

under 10X magnification?

1. Cell wall 2. Nucleus 3. Cytoplasm 4. Mitochondria

a. 1 and 3

b. 2 and 4

c. 1 and 4

d. 4

32. Which of the following is an example of a buffer solution?

A. CH3COOH + CH3COONH4
B. H2SO4 + CuSO4
C. CH3COONa + CH3COOH
D. NaCl + NaOH

33. Buffering capacity of any buffer would be maximum when its:

a. pH>pKa
b. pH<pKa
c. pH=7
d. pH=pKa

34. What is the function of the annealing temperature in PCR?

a) To separate DNA strands
b) To elongate new DNA strands
c) To bind primers to the template DNA
d) To deactivate DNA polymerase

35. Which factor affects the sensitivity of the Bradford assay for protein
quantification?
a. pH of the solution

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b. Temperature of the reaction
c. Protein concentration
d. All of the above