A mother from rural Louisiana brings her 4-year-old son to a pediatrician. Her son is intellectually disabled, and she hopes that genetic testing will help determine the cause of her son's condition. She had previously been opposed to allowing physicians to treat her son, but his impulsive behavior and learning disabilities are making it difficult to manage his care on her own. On exam, the child has a long, thin face with a large jaw, protruding ears, and macroorchidism. The physician also hears a high-pitched holosystolic murmur at the apex of the heart that radiates to the axilla. Which of the following trinucleotide repeats is most likely affected in this individual?
AGAA on chromosome 9
BCGG on the sex chromosome X
CCTG on chromosome 19
DCTG on chromosome 8
ECAG on chromosome 4
A 4-year-old child presents with developmental delay, ataxia, and inappropriate laughter. The parents undergo genetic testing to determine the cause of their child's symptoms. Results show no mutations in all three family members that would cause this constellation of symptoms. Karyotyping reveals no deletions, insertions, or gene translocations. However, methylation studies demonstrate abnormal imprinting patterns at the 15q11-q13 region. Based on these findings, the child is diagnosed with Angelman syndrome. Which of the following genetic mechanisms best describes the cause of this disorder?
AVariable expressivity
BUniparental disomy
CIncomplete penetrance
DAnticipation
EImprinting defect
A 5-year-old boy is brought to the physician because of behavioral problems. His mother says that he has frequent angry outbursts and gets into fights with his classmates. He constantly complains of feeling hungry, even after eating a full meal. He has no siblings, and both of his parents are healthy. He is at the 25th percentile for height and is above the 95th percentile for weight. Physical examination shows central obesity, undescended testes, almond-shaped eyes, and a thin upper lip. Which of the following genetic changes is most likely associated with this patient's condition?
AMitotic nondisjunction of chromosome 21
BMutation of FBN-1 gene on chromosome 15
CMicrodeletion of long arm of chromosome 7
DLoss of paternal gene expression on chromosome 15
EDeletion of Phe508 on chromosome 7
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