Huntington's disease is associated with an expanded CAG repeat on which chromosome?

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Multiple Choice

Huntington's disease is associated with an expanded CAG repeat on which chromosome?

Huntington's disease is caused by an expanded CAG trinucleotide repeat in the HTT gene, which sits on chromosome 4. Normal individuals typically have about 10–35 CAG repeats; when the repeats exceed roughly 36, the HTT protein gains a long polyglutamine tract that disrupts neuronal function, especially in the striatum, leading to the movement, cognitive, and behavioral signs of the disease. It’s autosomal dominant, so a single mutated copy is enough to cause the disorder, with a 50% risk to offspring. Larger repeat sizes often mean earlier onset due to anticipation, particularly with paternal transmission. Because the HTT gene is on chromosome 4, chromosome 4 is the correct chromosomal location—unlike the other chromosomes listed.

Huntington's disease is caused by an expanded CAG trinucleotide repeat in the HTT gene, which sits on chromosome 4. Normal individuals typically have about 10–35 CAG repeats; when the repeats exceed roughly 36, the HTT protein gains a long polyglutamine tract that disrupts neuronal function, especially in the striatum, leading to the movement, cognitive, and behavioral signs of the disease. It’s autosomal dominant, so a single mutated copy is enough to cause the disorder, with a 50% risk to offspring. Larger repeat sizes often mean earlier onset due to anticipation, particularly with paternal transmission. Because the HTT gene is on chromosome 4, chromosome 4 is the correct chromosomal location—unlike the other chromosomes listed.

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