Selected MCQ

Current Question
Which pH environment is required for optimal activity of lysosomal enzymes?
  • A. ~7.4
  • B. ~6.8
  • C. ~5.0
  • D. ~8.0
Correct Answer: C
Explanation:
Lysosomal hydrolases function best at an acidic pH around 5.0, maintained by proton pumps in the lysosomal membrane.
Related Question 1
Inheritance of human height, which is influenced by many genes and environmental factors, is an example of:
  • A. Codominance
  • B. Polygenic inheritance
  • C. Pleiotropy
  • D. Autosomal dominance
Correct Answer: B
Explanation:
Height is a quantitative trait determined by multiple genes (polygenes) and the environment, consistent with polygenic inheritance.
Related Question 2
In bacterial transcription, the σ (sigma) factor of RNA polymerase is required for:
  • A. RNA chain elongation
  • B. Recognizing promoter sequences
  • C. DNA replication
  • D. Termination of transcription
Correct Answer: B
Explanation:
The sigma subunit binds the promoter sequences (e.g., –10 and –35 regions) and directs RNA polymerase to initiate transcription at the correct site.
Related Question 3
During PCR, Taq DNA polymerase has an optimal extension temperature of approximately:
  • A. 50°C
  • B. 60°C
  • C. 72°C
  • D. 95°C
Correct Answer: C
Explanation:
Taq polymerase is most active at around 72°C, which is used for the extension step to synthesize new DNA strands.
Related Question 4
Which of the following components is *not* required for a standard PCR reaction?
  • A. Template DNA
  • B. DNA polymerase
  • C. Primers
  • D. DNA ligase
Correct Answer: D
Explanation:
PCR requires a thermostable DNA polymerase, primers, dNTPs, and template DNA. DNA ligase is not needed because PCR does not splice DNA fragments.
Related Question 5
Why does the lagging strand of DNA require more DNA ligase activity during replication than the leading strand?
  • A. It contains more errors to fix
  • B. It is synthesized more continuously
  • C. It is synthesized discontinuously in Okazaki fragments
  • D. It is shorter than the leading strand
Correct Answer: C
Explanation:
The lagging strand is made in short Okazaki fragments, each of which must be joined by DNA ligase. The leading strand is continuous and requires minimal ligation.