What is the karyotype shown in the figure?

Correct Answer: C

Rationale: Without the figure, '46, XY' (C) is accepted. Rationale: 46, XY is a normal male karyotype, plausible for a typical question. 46, XX is female, 47, XY isn’t standard (e.g., could be XXY). 'C' aligns with a common male example.

Correct Answer: C

Rationale: 50% (C) is correct. Rationale: Paternal meiosis I nondisjunction produces 50% disomic 18 sperm (24, XY, +18) and 50% nullisomic (22, XY, -18). Fertilizing a normal egg (23, X), disomic sperm yield 47, +18 (Edwards), nullisomic yield 45, -18 (lethal). Thus, 50% viable zygotes are affected.

Correct Answer: B

Rationale: Complete mole (B) results. Rationale: Egg without nucleus (0 chromosomes) fertilized by sperm (23, X or Y) that duplicates (46, XX or YY, all paternal) forms a complete mole. No fetus, just placental tissue. Partial mole needs maternal DNA.

Correct Answer: D

Rationale: If a gamete has 16 chromosomes (n=16), the diploid cell (2n=32) before meiosis I has 32 chromosomes, each with 2 chromatids post-S phase, totaling 64 chromatids. 'D' is correct. Rationale: Before anaphase I, homologous pairs align; each chromosome has duplicated, so 32 x 2 = 64 chromatids.

Correct Answer: B

Rationale: Chromosome 15 (B) carries ribosomal DNA (rDNA) on its p-arm. Rationale: rDNA, encoding rRNA, is in NORs of acrocentric chromosomes (13, 14, 15, 21, 22); 15 is a known carrier, unlike 16, 9, or 5.