ATI RN
Genetic Disorders in Pediatrics Questions
Question 1 of 5
The normal human chromosome diploid number is:
Correct Answer: C
Rationale: Humans have 46 chromosomes in diploid cells (2n=46).
Question 2 of 5
The most common cystic fibrosis mutation consists of:
Correct Answer: A
Rationale: The most common CF mutation is ΔF508, a 3-base-pair deletion in CFTR.
Question 3 of 5
If both parents are affected with the same autosomal recessive disorder then the probability that each of their children will be affected equals
Correct Answer: D
Rationale: If both parents are homozygous recessive (aa x aa), all offspring will be aa (100% affected).
Question 4 of 5
A full-term female newborn is examined shortly after birth. She appears to be small for gestational age, and she has excess skin on the nape of the neck and lymphedema of the hands and feet. Chromosomal analysis shows some cells with a normal 46,XY karyotype and some cells with a 45,X karyotype. Which of the following mechanisms best explains this cytogenetic abnormality?
Correct Answer: A
Rationale: Mosaicism (46,XY/45,X) arises from mitotic nondisjunction post-fertilization, losing an X or Y in some cells.
Question 5 of 5
In the following partial sequence of mRNA, a mutation of the template DNA results in a change in codon 91 to UAA. What type of mutation is it? | 88 | 89 | 90 | 91 | 92 | 93 | 94 | GUC | GAC | CAG | UAG | GGC | UAA | CCG |
Correct Answer: C
Rationale: UAG is a stop codon; changing codon 91 to UAA (another stop) is nonsense, causing premature termination.