ATI RN
Pediatric Genetic Questions
Question 1 of 5
Genetic anticipation is best described as
Correct Answer: A
Rationale: Genetic anticipation occurs in trinucleotide repeat disorders, where repeat expansion increases severity or lowers onset age in subsequent generations (e.g., Huntington’s disease). It’s not a disorder, nor tied to sex-specific penetrance or imprinting.
Question 2 of 5
Which of the following variants would you expect could to be most common:
Correct Answer: D
Rationale: C>T transitions are the most common DNA variants in humans, often due to deamination of cytosine to thymine, a frequent spontaneous mutation.
Question 3 of 5
A couple approached you because of a current pregnancy and a family history with phenylketonuria (PKU). The mother told you that her sister is affected with PKU and the father told you that his uncle is affected with PKU. You performed an ultrasound and the fetus turned out to be a female. What is the risk for the couple to have UNAFFECTED FEMALE with PKU? Assume a population frequency of 1/100? Note: PKU is an autosomal recessive disease.
Correct Answer: D
Rationale: Mother’s sister affected: mother’s carrier chance = 2/3. Father’s uncle affected: father’s carrier chance ≈ 1/100 (population frequency, distant relative). Both carriers = 2/3 × 1/100 = 2/300. Unaffected child = 3/4 (FF or Ff). Female = 1/2. Total = 2/300 × 3/4 × 1/2 = 1/6.
Question 4 of 5
Variants in tumor suppressors on the genetic level are----and on the phenotypic level are:---
Correct Answer: A
Rationale: Tumor suppressor mutations are recessive genetically (both alleles must be lost), but phenotypically dominant (one hit predisposes to cancer via second hit).
Question 5 of 5
A 6-month-old with unilateral retinoblastoma has genetic testing performed. The results of the tumor and blood analysis at the RBI locus are shown below (the photo is missing, but you don't need it anyway!). What is the likelihood that a future sibling WILL DEVELOP retinoblastoma?
Correct Answer: A
Rationale: Unilateral, sporadic retinoblastoma (no germline mutation) means siblings have a population risk (<1/20,000), approximated as <1%.