Selected MCQ

Current Question
Which eukaryotic RNA polymerase transcribes tRNA genes?
  • A. RNA polymerase I
  • B. RNA polymerase II
  • C. RNA polymerase III
  • D. RNA polymerase IV
Correct Answer: C
Explanation:
RNA Pol III transcribes tRNAs and 5S rRNA. Pol I makes most rRNAs, and Pol II makes mRNA and some snRNAs.
Related Question 1
The 5′ cap added to eukaryotic mRNAs is:
  • A. A string of adenine residues at the 5′ end
  • B. A modified guanosine (7-methylguanosine) linked 5′→5′
  • C. A poly-uridine sequence at the 3′ end
  • D. A phosphate group at the 5′ end
Correct Answer: B
Explanation:
The 5′ cap is a 7-methylguanosine joined via a 5′-to-5′ triphosphate linkage to the first nucleotide of the mRNA, protecting it from degradation and aiding translation.
Related Question 2
Which term describes genes that are located on the same chromosome and inherited together more often than by chance?
  • A. Linked genes
  • B. Epistatic genes
  • C. Polygenic genes
  • D. Independent genes
Correct Answer: A
Explanation:
Linked genes are near each other on the same chromosome. They tend to be inherited together, and their recombination frequency is less than 50%.
Related Question 3
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 4
Two genes exhibit a recombination frequency of 20% in genetic crosses. Which statement is most accurate?
  • A. The genes are likely on different chromosomes
  • B. The genes are roughly 20 map units apart on the same chromosome
  • C. The genes are so far apart that they assort independently
  • D. The genes are allelic variants of each other
Correct Answer: B
Explanation:
A recombination frequency of 20% indicates that the genes are linked (~20 centimorgans apart) on the same chromosome and not assorting completely independently.
Related Question 5
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.