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: A Set 1 (Questions 001 – 025)
1. The immunoglobulin fold is made up of:
a. Seven alpha helical segments
b. A beta barrel
c. A sandwich of two parallel beta sheets
d. A sandwich of two antiparallel beta sheets
Ans. (d). A sandwich of two antiparallel beta sheets
Immunoglobulin fold consists of a pair of β-sheets each built of antiparallel β-strands connected by a disulfide bridge. This β strands surrounds a central hydrophobic core. Immunoglobulin fold is one of the most predominant domains encoded by the human genome.
For more details refer: Biochemistry by Stryer, Ed.6, Chapter: 33, Immune systems, Page 951
2. RNA is analyzed for the location of hairpin folds. Which of the following sequence could form a mini-hairpin?
Ans. (a). AGGUUUCCU
This RNA molecule can loop around itself and can form double stranded structure due to the sequence complementarity. First A is complementary to last U, second and third nucleotide (UU) is complementary to CC. The middle UUU forms the junction of loop and they do not form the complementary hydrogen bonds.
3. Increasing the concentration of which of the following would most effectively anatomized the inhibition of protein synthesis by puromycin?
b. eIF2, GTP
Ans. (c). Aminoacyl-tRNA
Puromycin is an antibiotic obtained from a bacterium Streptomyces alboniger, which inhibit protein synthesis by specifically inhibiting the translation process. Puromycin inhibits protein translation by premature chain termination process. A part of the puromycin structurally mimics the 3’ end of Aminoacyl-tRNA molecule and hence they can enter to the ‘A’ site of ribosome and form a nascent peptide-puromycin adduct. This adducts formation results in the release of peptide from the ribosome. Puromycin compete with aminoacyl-tRNA for the A site of ribosome. Thus the inhibitory effect of puromycin can be theoretically overcome by increasing the concentration of the competitor, i.e., aminoacyl-tRNA.