Question

20. Protein amino acid side chains can hydrogen bond in the major groove of DNA, and discriminate between each of the four possible base pairs. In which one of the following groups of amino acids can all three members potentially be used in such DNA-protein recognition? A) Ala, Asn, Glu B) Arg. Gin, Leu C) Asn, Gin, Trp D) Asn, Glu, Lys E) Glu, Lys, Pro 21. Compared with DNA polymerase, reverse transcriptase: A) does not require a primer to initiate synthesis. B) introduces no errors into genetic material because it synthesizes RNA, not DNA. C) makes fewer errors in synthesizing a complementary polynucleotide. D) makes more errors because it lacks the 3' 5'proofreading exonuclease activity. E) synthesizes complementary strands in the opposite direction from 3' 5' complemenroofreading excom 3 -5'. 22. An integral membrane protein can be extracted with: A) a buffer of alkaline or acid pH. B) a chelating agent that removes divalent cations. c) a solution containing detergent. D) a solution of high ionic strength. E) hot water. 23. Which of the following is not usually essential for the catalytic activity of ribozymes? A) Correct base pairing B) Correct base sequence c) Correct interaction with protein D) Correct secondary structure E) Correct three-dimensional structure 24. The fluidity of a lipid bilayer will be increased by: A) decreasing the number of unsaturated fatty acids. B) decreasing the temperature. C) increasing the length of the alkyl chains. D) increasing the temperature. E) substituting 18:0 (stearic acid) in place of 182 (linoleic acid) 25. Alternative splicing may result in: A) a shift in the ratio of mRNA produced from two adjacent genes. B) attachment of the poly(A) tail to the 5' end of an mRNA C) inversion of certain exons in the final mRNA D) the production of the same protein from two different genes. E) the production of two distinct proteins from a single gene. 26. Which one of the following statements about E. coli RNA polymerase (core enzyme) is false? A) It can start new chains de novo or elongate old ones. B) It has no catalytic activity unless the sigma factor is bound. C) It uses nucleoside 5-triphosphates as substrates D) Its activity is blocked by rifampicin. E) Its RNA product will hybridize with the DNA template.

Answer 1

20. Option D is correct: Asn, Gln, Trp

21. Option D is correct. Because reverse transcriptase no proofreading ability, replication fidelity is less and is more error-prone

22. Option C is correct. It is relatively easier to extract integral proteins as they come out with the cell after lysis itself. Detergent containing buffers can be used for the extraction easily

23. Option C is correct

24. Option D is correct. High temperatures increase the fluidity as the intermolecular forces holding the membranes together weaken.

25.Option E is correct, Alternative splicing may result in two different proteins from a single gene

26.Option B is correct. Sigma factor helps in recognizing the promoter and has no role in catalytic activity