A cell is in GO phase. How many chromosomes does it have?

Correct Answer: A

Rationale: G0 is a quiescent phase with no division; a human somatic cell has 46 chromosomes (A). Rationale: G0 cells are diploid (2n=46), not haploid (23) or replicated (92, G2 phase). Answer matches normal somatic count.

Correct Answer: A

Rationale: 46, XX, del5p (A) causes Cri du Chat syndrome. Rationale: 5p deletion leads to severe phenotypes (cat-like cry, microcephaly). Balanced translocations (B, D) are normal; 22p deletion (C) is often benign (heterochromatic).

Correct Answer: C

Rationale: Paternal nondisjunction (C) causes 47, XYY. Rationale: Meiosis II nondisjunction in father produces YY sperm (24, YY), fertilizing X egg (23, X), yielding 47, XYY. Chimerism or UPD don’t fit; maternal nondisjunction gives XXY.

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: A

Rationale: Beta satellite DNA is on the p-arm of acrocentric chromosomes (e.g., 13, 14, 15, 21, 22). 'A' is correct. Rationale: These repetitive sequences are near nucleolar organizer regions (NORs) on short arms, distinct from centromeric alpha satellites.