Cells of the eye lens are:

Correct Answer: B

Rationale: Eye lens cells (epithelial) are diploid (2n=46), like most somatic cells. 'B' is correct. Rationale: Haploid (n=23) is for gametes, triploid (3n) and tetraploid (4n) are abnormal and rare in humans. Lens cells divide mitotically, maintaining diploidy.

Correct Answer: D

Rationale: 69, YYY (D) cannot occur in triploidy. Rationale: Triploidy (3n=69) results from dispermy or diploid gametes (e.g., XXY, XXX), but YYY requires three Y-bearing sperms, biologically implausible in humans.

Correct Answer: A

Rationale: 1 maternal, 1 paternal set (A) is normal. Rationale: Diploidy (2n=46) requires 23 chromosomes from egg and sperm; deviations (B-D) cause moles or lethality.

Correct Answer: A

Rationale: Dispermy (A) causes 69, XYY. Rationale: Two Y-bearing sperms (23, Y each) + egg (23, X) yield triploid 69, XYY; nondisjunction or endomitosis don’t fit.

Correct Answer: B

Rationale: Expressivity (B) is the variable degree of phenotype expression influenced by factors. Rationale: Unlike pleiotropy (A, multiple effects) or penetrance (C, all-or-none), expressivity explains severity variation (e.g., mild vs. severe in neurofibromatosis).