Question

Fragile X syndrome, characterized by mental retardation, is caused by which chromosomal change?
deletion
translocation
inversion
insertion

Answer 1

Fragile X syndrome is caused by a mutation in the FMR1 gene on the X chromosome. This mutation is known as a "CGG repeat expansion." It does not involve any of the chromosomal changes listed in the question (deletion, translocation, inversion, or insertion).