Which one of the following karyotypes is most likely to be found in normal human ovarian progenitor cell?

Correct Answer: C

Rationale: 46, XX (C) is normal for ovarian cells. Rationale: Ovarian progenitor cells (somatic) in females are diploid (2n=46, XX). 23, X is gametic; 46, XY is male; 22, Y is inviable.

Correct Answer: D

Rationale: Deletion of 16p (D) causes abnormalities (e.g., 16p11.2 deletion syndrome). Rationale: 13p, 14p, 15p are mostly heterochromatic (fewer genes), often benign when deleted; 16p has critical genes, leading to developmental issues.

Correct Answer: B

Rationale: Maternal meiosis I nondisjunction (B) is the most common cause of Down syndrome. Rationale: 90% of trisomy 21 cases are maternal, mostly MI errors (homologs fail to separate), linked to maternal age.

Correct Answer: C

Rationale: 2 maternal, 1 paternal sets (C) form a partial mole. Rationale: Triploidy (69, XXX or XXY) from dispermy or diploid egg retains some fetal tissue.

Correct Answer: C

Rationale: 45, XX, t(13;13) (C) is balanced, phenotypically normal. Rationale: Balanced translocation carriers (45 chromosomes) have normal gene dosage; others (XXY, X, +13) show syndromes.