Mock Test 5

Biochemistry Mock Test - 05

15:00

1. Which enzyme removes RNA primers during DNA replication in E. coli? A) DNA Polymerase III B) DNA Polymerase I C) DNA Ligase D) Primase

Correct: B. DNA Pol I has 5' to 3' exonuclease activity to remove primers.

2. Sigma factor ($\sigma$) in bacterial RNA polymerase is required for: A) Chain elongation B) Promoter recognition C) mRNA splicing D) Termination

Correct: B. It provides specificity for promoter binding.

3. Degeneracy of the genetic code means: A) One codon codes for many amino acids B) Many codons code for the same amino acid C) The code is different in every species D) Codons overlap during translation

Correct: B. For example, 6 different codons code for Leucine.

4. Which antibiotic mimics an aminoacyl-tRNA and cause premature termination? A) Tetracycline B) Streptomycin C) Puromycin D) Penicillin

Correct: C. Puromycin enters the A-site and stops protein synthesis.

5. Type II restriction endonucleases are useful in cloning because: A) They cut randomly B) They require ATP C) They cut at specific palindromic sites D) They only cut RNA

Correct: C. Their specificity allows precise DNA manipulation.

6. The 'TATA box' is a core promoter element found in: A) Bacteria B) Eukaryotes C) Viruses only D) Mitochondria only

Correct: B. Found around -25 to -30 bp in eukaryotic protein-coding genes.

7. Telomerase is a: A) DNA-dependent DNA polymerase B) RNA-dependent DNA polymerase C) DNA-dependent RNA polymerase D) Restriction enzyme

Correct: B. It is a specialized reverse transcriptase.

8. 5' Capping and 3' Polyadenylation of mRNA is essential for: A) DNA Replication B) mRNA stability and export C) Intron removal D) RNA interference

Correct: B. Protects from exonucleases and signals for transport.

9. The lac operon is 'off' (repressed) when: A) Lactose is present B) Lactose is absent C) Glucose is absent D) Allolactose binds to the repressor

Correct: B. Without lactose, the repressor blocks the operator.

10. If you start with 2 DNA molecules, how many will you have after 5 PCR cycles? A) 32 B) 64 C) 10 D) 128

Correct: B. $2 \times 2^5 = 2 \times 32 = 64$.