ATI RN
Pediatrics Genetics Questions
Question 1 of 5
Which P arm of the following chromosomes carries rDNA genes?
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.
Question 2 of 5
Which of the following genetic changes is associated with a female whose karyotype is 46, XY?
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.
Question 3 of 5
Which of the following karyotype is expected to be associated with abnormal phenotype [Note: 't' is translocation, and 'del' is deletion]:
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).
Question 4 of 5
47 XYY occurs due to:
Correct Answer: C
Rationale: Paternal nondisjunction (C) causes 47, XYY. Rationale: Meiosis II nondisjunction in father produces YY sperm (24, YY), fertilizing X egg (23, X), yielding 47, XYY. Chimerism or UPD don’t fit; maternal nondisjunction gives XXY.
Question 5 of 5
Cells of the eye lens are:
Correct Answer: B
Rationale: Eye lens cells (epithelial) are diploid (2n=46), like most somatic cells. 'B' is correct. Rationale: Haploid (n=23) is for gametes, triploid (3n) and tetraploid (4n) are abnormal and rare in humans. Lens cells divide mitotically, maintaining diploidy.