Trisomy 47,XYY is a syndrome with signs and symptoms that range from being barely noticeable to learning disabilities, speech delay, low muscle tone. How would you expect this syndrome to have occurred?

Correct Answer: D

Rationale: Paternal nondisjunction causes 47, XYY. Rationale: Nondisjunction in paternal meiosis II results in YY sperm (24, YY), fertilizing an X egg (23, X), yielding 47, XYY. Dispermy or endomitosis would yield triploidy or tetraploidy.

Correct Answer: A

Rationale: Chromosome 22 is acrocentric, with a very short p-arm and centromere near one end. 'A' is correct. Rationale: Human acrocentric chromosomes (13, 14, 15, 21, 22) have nucleolar organizer regions on their p-arms; 22 fits this pattern, unlike metacentric (central centromere) or telocentric (end centromere).

Correct Answer: C

Rationale: G-banding (C) stains heterochromatin dark (G-positive) and euchromatin light. Rationale: Giemsa stains AT-rich, gene-poor heterochromatin dark, while GC-rich, gene-active euchromatin stays light, standard for karyotyping.

Correct Answer: C

Rationale: Nondisjunction in meiosis I (MI, C) affects all daughter cells. Rationale: MI separates homologs; failure means all gametes get abnormal chromosome numbers (e.g., 24 or 22), unlike MII (sister chromatids, half affected).

Correct Answer: D

Rationale: 1/6 ( missing in OCR) is correct. Rationale: 45, XY, t(14;21) produces 6 gametes: normal, t(14;21), 14, 21, null 14, null 21. With 46, XX, only 21+t(14;21) yields 47, +21 (Down), 1/6 chance.