Gene Organization, Replication and Repair — DU B. Sc. (Hons) Biochemistry Previous Year Question Papers

There are 6 questions. Attempt 4 questions in all. 1. (A) Give the functions of the following proteins : - (d) Single strand DNA binding proteins (e) Dam methylase (B) State True or False and explain : (a) Eukaryotic chromosomes are linear and free from torsional strain. (b) Sliding clamps increase DNA polymerase processivity. (e) DNA replication is conservative in nature. (d) Microsatellites are mutational host spots that can serve as biomarkers for diseases. (e). Linking number of a DNA molecule with double strańded breaks equals to Iwist." 5,10 2. Differentiate between the following : (b) Recombination and Transposition (d) Translesion Repair and NHEJ : (e) Serine and Tyrosine recombinase 5x3 3. (A) What is the mechanism of replication initiation in prokaryotes and eukaryotes ? - (B) Explain two mechanisms of direct repair of DNA. (C) Diagrammatically explain the roles of various domains of DNA polymerase 4. (A) Describe the features of Watson-Crick model of DNA structure and explain the underlying basis for its flexibility. (B) Explain how the following chemicals or conditions cause mutations : (c) Deamination of adenine (d) Ethidium bromide (e). Gamma radiation (C) Explain the key steps of Homologous recombination. Draw the Holliday 5. (A) What are Okazaki fragments? Explain leading and lagging strand synthesis with the help of a diagram. (B) Name the scientist who invented the Ames Test. Explain its principle and - state its application. (C) Explain the role of telomerases in eukaryotic DNA replication. 6,5,4 6. Write short notes on the following: (a) Replication slippage (c) Xeroderma pigmentosum (d) Topoisomerase inhibitors (e) Split genes and satellite DNA. 3x5