A child has just been diagnosed with fragile X syndrome. What is fragile X syndrome?
A) A chromosomal defect affecting females only
B) A chromosomal defect that follows the pattern of X-linked recessive disorders
C) The second most common genetic cause of cognitive impairment
D) The most common cause of noninherited cognitive impairment

Question

Quizplus · Accepted Answer

Fragile X syndrome is the second most common cause of cognitive impairment after Down syndrome. Fragile X primarily affects males, and follows the inheritance pattern of X-linked dominant with reduced penetrance. This is in distinct contrast to the classic X-linked recessive pattern in which all carrier females are normal, all affected males have symptoms of the disorder, and no males are carriers.

A Child Has Just Been Diagnosed with Fragile X Syndrome