A 35-year-old man who works at a facility processing highly radioactive substances accidentally receives a high, whole-body dose of ionizing radiation estimated to be 1500 rads (15 gray). He dies 1 week later. At autopsy, histologic examination of the skin shows scattered, individual epidermal cells with shrunken markedly eosinophilic cytoplasm and pyknotic, fragmented nuclei. These morphologic changes most likely indicate which of the following processes?

Correct Answer: A

Rationale: High radiation induces apoptosis (programmed cell death), seen as shrunken, eosinophilic cells with fragmented nuclei.

Correct Answer: C

Rationale: In G2 phase, after DNA replication (S phase), each of the 46 chromosomes consists of 2 sister chromatids (double-stranded DNA molecules). Thus, 92 double-stranded molecules exist. Answer 'C' (92) is correct. Rationale: Each chromosome’s chromatids are identical double helices, totaling 92 in a diploid human cell (2n=46).

Correct Answer: A

Rationale: Cytogenetics (A) studies chromosomes and cell division. Rationale: Cytology is broader (cell biology), and pedigree is inheritance charting. Cytogenetics focuses on karyotypes and meiosis/mitosis.

Correct Answer: C

Rationale: 45, XY, t(14,21) (C) is a balanced Robertsonian translocation, phenotypically normal. Rationale: 46, 0Y is inviable (no X), trisomy 14 is lethal, but t(14;21) carriers have normal gene content despite 45 chromosomes.

Correct Answer: D

Rationale: 1/2 (D) is approximate. Rationale: Balanced translocation (e.g., t(11;22)) with normal partner yields 4 gamete types via adjacent/alternate segregation: 50% balanced (normal or carrier), 50% unbalanced (duplication/deletion), risking abnormal fetuses. Exact risk varies, but 1/2 is typical.