ATI RN
Pediatric Genetics Questions
Question 1 of 4
Prader-Willi syndrome may occur from a uniparental maternal disomy of chromosome 15. There is no parental chromosome 15. The expressed phenotype is an example of
Correct Answer: C
Rationale: Prader-Willi results from loss of paternal 15q11-13 (via deletion or maternal uniparental disomy). This is imprinting, where gene expression depends on parental origin. Penetrance, expressivity, mitochondrial inheritance, and nondisjunction don’t apply.
Question 2 of 4
A couple are both tested, the father is affected with cystic fibrosis and the mother is a carrier of cystic fibrosis gene. What is the chance that they will have a HOMOZYGOUS NORMAL MALE?
Correct Answer: C
Rationale: Father (affected, ff) contributes f. Mother (carrier, Ff) contributes F or f (1/2 each). Child genotypes: Ff (carrier) or ff (affected). No FF (homozygous normal) is possible, so chance = 0. Sex (male) doesn’t change this.
Question 3 of 4
In an experiment gene X was over expressed in neoplastic cell. Consequently, it acquired malignant traits. Gene X is most likely:
Correct Answer: D
Rationale: Proto-oncogenes, when overexpressed, drive malignancy (e.g., cell proliferation). Tumor suppressors inhibit cancer when functional. Cytoskeletal genes and noncoding sequences don’t typically confer malignancy.
Question 4 of 4
A variant that results in genetic mosaicism is:
Correct Answer: B
Rationale: Mosaicism arises from somatic variants (post-zygotic mutations), not germline (present in all cells) or other types.