Tools of Genetic Engineering — DU B. Sc. (Hons) Biochemistry Previous Year Question Papers

There are six questions in this question paper. 1. (a) Explain the following : DNA molecules are treated with alkaline phosphatase before ligation. (ii) Antibiotic resistance genes are used as selectable markers. (iii) Plasmid vectors are not suitable for cloning large DNA fragments. (io) All eukaryotic genes cannot be expressed in E. coli. (u) DNA polymerase I may not be the best enzyme for PCR. (Ul) Lamda phage vectors cannot package more than 24kb DNA during in vitro packaging. (b) Give the contribution of the following : (i) Smith and Nathans (iii) Bolivar and Rodriguez. 12,3 (a) Differentiate between the following : (i) Natural promoters and hybrid promoters (b) Give the salient features of Ti-plasmid-based vectors. 9,6 (a) You are given a plasmid vector that has a unique site BamHI enzyme (5'G/GATCC-3'). Cut this vector with BamHI. Now cut a gene of interest with the same enzyme and ligate them together to form a recombinant molecule. Show all the steps diagrammatically. (b) What are the parameters that should be kept in mind while designing primers for PCR ? (c) Describe T7 promoter-based expression system. 5,5,5 4. (a) Discuss Sangers's dideoxy method of DNA sequencing. (b) Describe the principle of blue-white selection for screening recombinant clones. (c) Explain how antibiotic resistance can be used to differentiate between transformants and recombinants ? 6,5,4 (a) With the help of reactions show how these enzymes are used in genetic engineering: (i) Reverse transcriptase (b) Draw the DNA sequencing profile (slab gel) obtained by Sanger's method, of the given strand of DNA 5'-ACC TTC CAT GCC GAC TTT 6. Write short notes on the following : (b) Genomic library (c) Fusion tags. 5,5,5