Park has found that her patient, Ye-Jun, has a defect in a gene on the X chromosome of his 23rd pair, resulting in a deficiency of a protein needed for brain development. Ye-Jun most likely suffers from __________.
A) fragile X syndrome
B) Down syndrome
C) cretinism
D) fetal alcohol syndrome

Question

Quizplus · Accepted Answer

Fragile X syndrome is caused by a defect in the FMR1 gene on the X chromosome, which results in a deficiency of a protein needed for brain development. This is consistent with the information provided in the question stem. Down syndrome is caused by an extra copy of chromosome 21, and is not related to a defect on the X chromosome. Cretinism is caused by a deficiency of thyroid hormone, and fetal alcohol syndrome is caused by maternal consumption of alcohol during pregnancy. Neither of these conditions are related to a defect on the X chromosome.

Park Has Found That Her Patient, Ye-Jun, Has a Defect