46 XX male syndrome is a rare condition, described by De la Chapelle et al. in 1964 where the individual has phenotypically male characteristics. It occurs in one out of every 20,000-25,000 newborn males. This condition could be related to:

Correct Answer: C

Rationale: SRY gene (C) causes 46, XX males. Rationale: SRY translocation from Y to X or autosome in XX individuals triggers male development despite no Y chromosome. Turner is 45, X; Rb is unrelated (retinoblastoma).

Correct Answer: D

Rationale: A homologous pair in metaphase I has 2 chromosomes, each with 2 chromatids (4 double-stranded DNA molecules total). (4) is correct. Rationale: Post-S phase, each chromosome duplicates; a pair (e.g., chromosome 1 from mom and dad) has 4 double helices before separation.

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.