Biochem 223-final 2005

(B. Sc. Biochemistry) Fourth Semester 2005 Subject: Biochem 223 (Molecular Biology)

Full Marks: 100 Pass Marks: 45 Time: 3 hours

Candidates are required to give their answers in their own words as far as practicable. The figure in the margin indicates full marks. (3× ×14 = 42)

Group (A) Long Questions (Any three)

1. Describe the significance of homologous recombination process. How do RecA and RecBCD perform homologous recombination? 2. Describe how a cell synthesizes RNA depending on DNA. 3. Describe how eukaryotic proteins are directed to and modified in endoplasmic reticulum? 4. Describe E. coli tryptophan operon. (6× ×7 = 42)

Group (B) Short Questions: (Any six) 1. 2. 3. 4. 5. 6. 7. 8.

How does topoisomerase II change linking number in chromosome? Compare various DNA polymerases found in E. coli. How does a yeast cell modify mRNA on its 5' –end? Describe homing activities of introns. Describe translation initiation in in E. coli. Describe various aspects of energetics of peptide bond. Describe various structure of functional motifs of DNA binding proteins. Why most of eukaryotic proteins are regulated positively?

Group (C) Very Short Questions: (Any eight) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

What are introns? Describe the structural features of nucleosome. How a chemical substance is characterized as mutagen? How are tRNA bases modification? How are retroviruses related to cancer and AIDS? Discuss the activities of telomerases. How can you say that the genetic code is non overlapping? Describe eukaryotic DNA polymerases. What do you mean by Wobble hypothesis? Point out potential steps of gene regulation. Define operon. What is its significance? What is Genetic engineering? Give some of its applications. ***

(2× ×8 = 16)