Previous Year Questions
2025
ZOOLOGY — HONOURS
Paper : DSCC-7
(Molecular Biology)
Full Marks : 75
Section - A
1. Answer any ten questions :
2 × 10
(a) What is Hyperchromic shift?
(b) Write the differences between A-DNA and B-DNA in the term of number of base pairs per helical turn and helical diameter.
(c) In an organism, 17% of the bases of its double stranded DNA is Cytosine. Calculate the percentage of other three bases present in its DNA.
(d) What do you mean by conservative and dispersive model of replication?
(e) What are Okazaki fragments?
(f) Why the replicon in prokaryotes are generally larger than that of eukaryotes?
(g) Write two differences between DNA polymerase I and DNA polymerase III.
(h) What is TATA box? What is its function?
(i) Comment on importance of enhancer sequence.
(j) State the importance of Poly (A) tail of mRNA.
(k) Differentiate between Induction and Repression.
(l) What is IPTG? What is its function in study of operons?
(m) Explain the role of SDS in SDS PAGE.
(n) Write two uses of PCR.
(o) Why transcription-translation coupling is possible only in prokaryotes but not in eukaryotes?
Section - B
2. Write short notes on (any three) :
5 × 3
(a) Watson and Crick Model of the Three-Dimensional Structure of DNA
(b) SOS repair
(c) Principle and use of Reverse Transcriptase-PCR
(d) tRNA charging
(e) Spliceosome and its function.
Section - C
Answer any four questions.
3. (a) Describe the Clover-leaf structure of tRNA with diagram.
(b) Describe the role of the following proteins in replication : (i) SSB (ii) Primase.
(c) What is replication licensing factor? (3+2)+2+3
(b) Describe the role of the following proteins in replication : (i) SSB (ii) Primase.
(c) What is replication licensing factor? (3+2)+2+3
4. (a) What is 'end replication problem'?
(b) Discuss the role of Sigma (σ) factor in Transcription.
(c) Describe Rho-dependent Termination with appropriate diagram.
(d) What is the role of Shine-Dalgarno sequence in formation of initiation complex? 2+2+4+2
(b) Discuss the role of Sigma (σ) factor in Transcription.
(c) Describe Rho-dependent Termination with appropriate diagram.
(d) What is the role of Shine-Dalgarno sequence in formation of initiation complex? 2+2+4+2
5. (a) Write the role of EF-Tu and EF-Ts protein in translation. What is the role of peptidyl transferase enzyme?
(b) Describe the process of mRNA polyadenylation with diagram. (3+2)+(3+2)
(b) Describe the process of mRNA polyadenylation with diagram. (3+2)+(3+2)
6. (a) Describe the positive regulation of the lac operon.
(b) A partial diploid strain (lacI+ lacO+ lacZ− lacY+ / lacI− lacO+ lacZ+ lacY−) has normal operators and normal promoters. Explain the fate of beta-galactosidase and permease transcription in such partial diploid in the presence of the inducer.
(c) What are the effect of lacIs (superrepressor) and lacOc (operator-constitutive) mutations? 4+3+(1½+1½)
(b) A partial diploid strain (lacI+ lacO+ lacZ− lacY+ / lacI− lacO+ lacZ+ lacY−) has normal operators and normal promoters. Explain the fate of beta-galactosidase and permease transcription in such partial diploid in the presence of the inducer.
(c) What are the effect of lacIs (superrepressor) and lacOc (operator-constitutive) mutations? 4+3+(1½+1½)
7. (a) Describe the steps of formation of transcription initiation complex in eukaryotes.
(b) What is the role of RecBCD and RecA protein in DNA repair?
(c) How histone acetylation regulates gene expression? 3+(2½+2½)+2
(b) What is the role of RecBCD and RecA protein in DNA repair?
(c) How histone acetylation regulates gene expression? 3+(2½+2½)+2
8. (a) Describe the significance of three different temperatures in a general PCR cycle. What is the importance of Taq Polymerase?
(b) What is the importance of Blocking step in Western blot?
(c) What do you mean by Stacking and Resolving gel in SDS PAGE? (3+2)+2+3
(b) What is the importance of Blocking step in Western blot?
(c) What do you mean by Stacking and Resolving gel in SDS PAGE? (3+2)+2+3
9. (a) Briefly describe miRNA mediated gene silencing.
(b) What is DNMT? Mention its role in DNA methylation and gene expression.
(c) Why leader sequence is important for 'trp' operon? 5+(1+2)+2
(b) What is DNMT? Mention its role in DNA methylation and gene expression.
(c) Why leader sequence is important for 'trp' operon? 5+(1+2)+2
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