CSIR Genetics MCQ questions part -5

41. Who demonstrated that genes are located on chromosomes?
(a) Morgan (b) Meselson and Stahl
(c) Chargaff (d) Franklin

42. In Griffith’s experiments, a harmless variant of S. pneumoniae became pathogenic when mixed with a heat-killed pathogenic variant as a result of

(a) conjugation (b) transduction
(c) mutation (d) transformation

43. In an important experiment, bacteriophages were allowed to infect bacteria. In the first trial, the phages used contained radioactive DNA, and radioactivity was detected in the bacteria. Next, other phages containing radioactive protein were allowed to infect bacteria, and no radioactivity was detected in the bacteria. When the experimenters compared the results of these two trials, they concluded that
(a) genes are made of DNA
(b) bacteriophages can infect bacteria
(c) DNA is made of nucleotides
(d) genes carry information for making proteins

44. A geneticist raised a crop of T2 bacteriophages in a medium containing radioactive phosphorus, so that the DNA of the bacteriophages was labeled with radioactivity. The labeled phages were then allowed to infect nonradioactive bacteria. In a few hours, these bacteria burst open, releasing many bacteriophages. Some of these phages contained labeled
(a) DNA
(b) RNA
(c) protein
(d) DNA and protein only

45. Scientists have discovered how to put together a bacteriophage with the protein coat of phage T2 and the DNA of phage T4. If this composite phage were allowed to infect a bacterium, the phages produced in the host cell would have
(a) the protein of T2 and the DNA of T4
(b) the protein of T4 and the DNA of T2
(c) the protein and DNA of T2
(d) the protein and DNA of T4

46. Chargaff found that for DNA
(a) the ratio of A to C is close to 1:1 and the ratio of G to T is close to 1:1
(b) the ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1
(c) the ratio of A to G is close to 1:1 and the ratio of T to C is close to 1:1
(d) A + T = G + C

47. The X-ray diffraction studies conducted by ______ were key to the discovery of the
structure of DNA.

(a) McClintock (b) Franklin
(c) Meselson and Stahl (d) Chargaff

48. Which of the following is not true of DNA?
(a) A pairs with T and G pairs with C
(b) Nitrogen bases are 0.34 nm apart on a DNA strand
(c) The double helix is 2.0 nm wide
(d) The double helix is 3.4 nm wide

49. Which of the following is correct?
(a) A forms 2 hydrogen bonds with G; T forms 3 hydrogen bonds with C
(b) A forms 3 hydrogen bonds with T; G forms 2 hydrogen bonds with C
(c) A forms 2 covalent bonds with T; G forms 3 covalent bonds with C
(d) A forms 2 hydrogen bonds with T; G forms 3 hydrogen bonds with C

50. Which of the following is not needed for DNA replication?
(a) ribosomes (b) DNA
(c) nucleotides (d) enzymes

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