Biotechnology Eligibility Test (BET) for DBT JRF Award (2012-13)
Previous Year Question Papers with Answer Key, Explanations & References
Government of India, Ministry of Science & Technology
Department of Biotechnology, New Delhi
PART: B Set 3 (Questions 51 – 100)
51. Suppressor tRNA mutations are those in which
a. Transcription of tRNA genes is suppressed
b. Translation form mRNA is suppressed due to absence of tRNA
c. Amino acid is incorporated in place of a stop codon due to mutation in anticodon region of tRNA
d. Charging of tRNA with cognate amino acids is suppressed due to mutation in amino acyl tRNA synthase enzyme
Ans. (c)
Suppressor tRNA: also called as nonsense suppressor, due to the suppressor tRNA mutations, an amino acid is incorporated into the stop codon due to mutation in the anticodons of tRNA so that the releasing factors of translation cannot binds to the complex and the translocation process continues.
52. Which of the following media is best suited for the selective growth of E. coli with genotype: Str+ His- leu- lys-?
a. Minimal medium with thiamine, histidine, leucine and lysine
b. Luria agar
c. Minimal medium with thiamine and streptomycin
d. Minimal medium with thiamine, histidine, leucine, lysine and streptomycin
Ans. (d)
Minimal medium: media that contains minimum nutrients possible for bacterial growth, usually without the presence of amino acids. They used by microbiologists and geneticists to grow “wild type” microorganisms and to select microbes against recombinants.
In the question, the given bacterium is mutated for Histidine, Leucine, and lysine and it has got an antibiotic resistant gene Str+.
53. Which of the following amino acid is coded by maximum number of codons?
a. Leucine
b. Tryptophan
c. Valine
d. Alanine