A 31-year-old man has a unilateral breast lump. A biopsy is performed, and the pathology report, surprisingly, shows an early-stage carcinoma. The man’s family history reveals no history of breast cancer. What would the physician be most likely to advise?

Correct Answer: B

Rationale: Male breast cancer suggests possible Klinefelter syndrome (47,XXY), warranting a karyotype to assess sex chromosomes.

Correct Answer: B

Rationale: Chromosome 15’s p-arm carries ribosomal DNA (rDNA) genes, part of the nucleolar organizer regions (NORs) on acrocentric chromosomes (13, 14, 15, 21, 22). Answer 'B' is correct. Rationale: rDNA encodes ribosomal RNA, located in the short arms of these chromosomes, with 15 being a known carrier.

Correct Answer: A

Rationale: G0 is a quiescent phase with no division; a human somatic cell has 46 chromosomes (A). Rationale: G0 cells are diploid (2n=46), not haploid (23) or replicated (92, G2 phase). Answer matches normal somatic count.

Correct Answer: A

Rationale: 46, XY female indicates SRY mutation (A). Rationale: SRY on Y determines maleness; mutations prevent testis development, resulting in female phenotype despite XY karyotype. Monosomy X is 45, X; Triple X is 47, XXX.

Correct Answer: A

Rationale: 46, XX, del5p (A) causes Cri du Chat syndrome. Rationale: 5p deletion leads to severe phenotypes (cat-like cry, microcephaly). Balanced translocations (B, D) are normal; 22p deletion (C) is often benign (heterochromatic).