ATI RN
Pediatric Genetic Questions
Question 1 of 4
A newborn infant is noted to have dysmorphic features. The pregnancy was complicated by breech presentation, decreased fetal movements, and polyhydramnios. The child demonstrates hypotonia, a flat face, flattened occiput, epicanthal folds, and abdominal distention. The most likely cause of this child's dysmorphology is
Correct Answer: D
Rationale: Trisomy 21 (Down syndrome) matches these features: hypotonia, flat face, epicanthal folds, and polyhydramnios due to GI issues (e.g., duodenal atresia). Trisomy 13 and 18 (Edwards) have distinct, more severe anomalies. Trisomy 8 is rarer and less consistent with this presentation.
Question 2 of 4
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 3 of 4
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 4 of 4
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%.