Selected MCQ

Current Question
DNA methylation at CpG islands in gene promoters typically leads to:
  • A. Transcriptional activation
  • B. Transcriptional silencing
  • C. Increased mutation rate
  • D. Immediate DNA repair
Correct Answer: B
Explanation:
Methylation of cytosines in promoters condenses chromatin and represses transcription, silencing the gene.
Related Question 1
Activation of a Gs protein-coupled receptor typically leads to stimulation of which enzyme to increase intracellular cAMP?
  • A. Protein kinase C
  • B. Adenylyl cyclase
  • C. Phosphodiesterase
  • D. Guanylyl cyclase
Correct Answer: B
Explanation:
Gs α-subunit activates adenylyl cyclase, which converts ATP to cAMP, raising second-messenger levels.
Related Question 2
Alternative splicing occurs during gene expression at the level of:
  • A. DNA replication
  • B. Transcription initiation
  • C. Pre-mRNA processing (RNA splicing)
  • D. Protein folding
Correct Answer: C
Explanation:
Alternative splicing of pre-mRNA allows different exons to be joined or skipped, producing multiple mRNA variants from one gene during RNA processing.
Related Question 3
In gene therapy using a viral vector, what is a major concern related to using retroviruses?
  • A. They cannot infect human cells
  • B. They only integrate into mitochondrial DNA
  • C. Insertional mutagenesis by random integration into the host genome
  • D. They cannot carry large genes
Correct Answer: C
Explanation:
Retroviral vectors integrate randomly into the host genome, risking insertional mutagenesis (disrupting host genes), which can cause cancer or other issues.
Related Question 4
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 5
In tissue engineering, a scaffold material must typically be:
  • A. Non-biodegradable only
  • B. Biocompatible and biodegradable
  • C. Made of metal only
  • D. Radioactive
Correct Answer: B
Explanation:
Tissue scaffolds are usually biocompatible (non-toxic, no immune response) and biodegradable so that they eventually degrade as new tissue forms in the scaffold’s place.