The heritable disorder fragile X syndrome, a major cause of intellectual disability, is caused by
A)production of enzymes that break the phosphate backbone.
B)UV light.
C)X-rays.
D)the presence of an extra X chromosome in the sperm or egg.
E)the expansion of a region of trinucleotide repeats.

Question

Quizplus · Accepted Answer

Fragile X syndrome is caused by the expansion of a CGG trinucleotide repeat affecting the FMR1 gene on the X chromosome, not by the other factors listed.

The Heritable Disorder Fragile X Syndrome, a Major Cause of Intellectual