Molecular Biology of the Cell — DU B.Sc. (Hons.) Botany Previous Year Question Papers

3. Attempt four questions in all. 4. All parts of questions must be answered together. 1. (a) Define the following (any five) : (1×5=5) (i) Transcription unit (ii) Consensus sequence (iii) Enhancer (vi) Promoter clearance (b) Fill in the blanks. (1x5=5) (i) The process of reformation of double helices from the denatured complementary single strands of DNA is called (ii) Positive charge in histone molecules are imparted due to the presence of high percentage of and residues. (iii) The Clover leaf model of tRNA structure was proposed by (iv) The is responsible for recognition of promoter during prokaryotic transcription. (v) Genes specifying proteins or enzymes that are not the part of the regulatory elements in an operon are called (c) Expand the following (any five) : (1x5=5) 2. Write a short note on any three of the following. Draw proper diagrams wherever necessary. (1) Wobble Hypothesis. (iv) John Cairn's experiment describing the Theta mode of replication. (V) Transcription termination in eukaryotes 3. Differentiate between the following (any three: (ii) Splicing in group I and group II introns. (iii) Inducible and repressible system. (iv) RNA Pol-1, RNA Pol-Il and RNA Pol-III 4. (a) Elaborate the three possible modes of DNA replication and discuss as how Moselson and Stahl deduced the most accurate and accepted model. (b) Elaborate the process of transcription initiation in prokaryotic and eukaryotic systems. (8) 5. (a) "Nearly all three major forms of RNA molecules are involved in some aspect during translation". Elaborate the statement and discuss in details the components of translational machinery. (7) (b) Define the term "spliceosome" '. Elaborate various molecular complexes associated in the assembly of spliceosome and the mechanism of splicing via spliceosome complex. (8) 6. (a) Define RNA interference. Give the steps involved in post transcriptional gene silencing by (b) Elaborate the various types of promoter elements in prokaryotic and eukaryotic genes. Describe at least two key features that distinguish a eukaryotic enhancer element form a promoter. (8)