A fatal central nervous system disorder caused by a copy number variation-more than 35 repetitions of a particular set of three base pairs-is _____.
A) Down syndrome
B) nearsightedness
C) fragile X syndrome
D) Huntington's disease

Question

Quizplus · Accepted Answer

The disorder described in the question is Huntington's disease, which is caused by a CAG trinucleotide repeat expansion in the huntingtin gene. This expansion leads to the production of a mutated form of the huntingtin protein, which accumulates in certain neurons in the brain and causes their degeneration, leading to symptoms such as involuntary movements, psychiatric disturbances, and cognitive decline. Down syndrome is a chromosomal disorder caused by an extra copy of chromosome 21, while fragile X syndrome is caused by a mutation in the FMR1 gene that leads to a reduced production of the fragile X mental retardation protein (FMRP) and is characterized by intellectual disability, behavioral problems, and physical features such as a long face and large ears. Nearsightedness, or myopia, is a refractive error of the eye that causes distant objects to appear blurry.

A Fatal Central Nervous System Disorder Caused by a Copy