Chronic myeloid leukemia is caused by?

Correct Answer: A

Rationale: CML is caused by t(9;22) (Philadelphia chromosome, A). Rationale: BCR-ABL1 fusion drives uncontrolled myeloid proliferation. Trisomy 18 and 13 cause Edwards and Patau syndromes, not CML.

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.

Correct Answer: B

Rationale: Duplication (B) adds genetic material. Rationale: Deletion removes, translocations rearrange (no net gain), while duplication increases gene copies, potentially causing phenotypes like Charcot-Marie-Tooth.