Selected MCQ

Current Question
Pluripotent stem cells are characterized by their ability to:
  • A. Differentiate into all cell types, including extraembryonic membranes
  • B. Differentiate into any cell type of the body (but not extraembryonic tissues)
  • C. Self-renew indefinitely but only become one cell type
  • D. Be harvested from adult muscle tissue
Correct Answer: B
Explanation:
Pluripotent stem cells (like embryonic stem cells) can form any body cell type (endoderm, mesoderm, ectoderm) but cannot form an entire organism (unlike totipotent zygotes).
Related Question 1
Phenylketonuria (PKU) is inherited as an autosomal recessive trait. If two carriers have a child, what is the probability the child will be unaffected (no mutant alleles)?
  • A. 100%
  • B. 75%
  • C. 50%
  • D. 25%
Correct Answer: B
Explanation:
For two carriers (Aa × Aa), the offspring genotype ratio is 1 AA: 2 Aa: 1 aa. 75% (AA + Aa) are unaffected (though 50% are carriers).
Related Question 2
In flow cytometry, cells are labeled with fluorescent antibodies and passed in a stream through a laser. This technique primarily measures:
  • A. Cell size and internal complexity
  • B. DNA sequence variants
  • C. Protein structure by X-ray diffraction
  • D. Glycolytic activity
Correct Answer: A
Explanation:
Flow cytometry measures light scattering (size and granularity) and fluorescence from labeled markers, allowing rapid analysis of cell populations (size, complexity, marker expression).
Related Question 3
Which method uses an electrical pulse to introduce DNA into cells?
  • A. Microinjection
  • B. Electroporation
  • C. Lipofection
  • D. Ultracentrifugation
Correct Answer: B
Explanation:
Electroporation applies a brief high-voltage pulse to permeabilize cell membranes, transiently allowing DNA uptake.
Related Question 4
Huntington’s disease, characterized by neurodegeneration and anticipation, is inherited in which manner?
  • A. Autosomal recessive
  • B. Autosomal dominant
  • C. X-linked recessive
  • D. Mitochondrial
Correct Answer: B
Explanation:
Huntington’s disease is autosomal dominant (one mutant allele is sufficient) and shows anticipation due to CAG repeat expansion, but inheritance is strictly dominant.
Related Question 5
A mother carries a mutated X-linked recessive gene but is unaffected. What is the probability that a son of hers will express the trait?
  • A. 0%
  • B. 25%
  • C. 50%
  • D. 100%
Correct Answer: C
Explanation:
A carrier mother (X^mX) has a 50% chance of passing the mutant X to a son. If he receives it, he will express the recessive trait (since sons inherit only one X chromosome).