What trinucleotide repeat disorder is associated with the CGG sequence?

What trinucleotide repeat disorder is associated with the CGG sequence?

• A. Lynch syndrome
• B. Fragile X syndrome
• C. Duchenne muscular dystrophy
• D. Huntington disease

Answer: (B)

The trinucleotide repeat disorder associated with the CGG sequence is Fragile X syndrome. This condition arises from an expansion of repeated CGG sequences within the FMR1 gene located on the X chromosome. Normally, a healthy individual might have 5 to 44 CGG repeats, while in individuals with Fragile X syndrome, this region can be expanded to over 200 repeats, leading to a silencing of the FMR1 gene and resulting in cognitive impairment, behavioral issues, and physical features such as an elongated face and large ears. Lynch syndrome, also known as hereditary nonpolyposis colorectal cancer (HNPCC), is associated with mutations in mismatch repair genes but is not a trinucleotide repeat disorder. Duchenne muscular dystrophy is caused by mutations in the dystrophin gene and does not involve repeat expansions. Huntington disease involves an expanded CAG repeat in the HTT gene, which is distinct from the CGG repeat that characterizes Fragile X syndrome.

The trinucleotide repeat disorder associated with the CGG sequence is Fragile X syndrome. This condition arises from an expansion of repeated CGG sequences within the FMR1 gene located on the X chromosome. Normally, a healthy individual might have 5 to 44 CGG repeats, while in individuals with Fragile X syndrome, this region can be expanded to over 200 repeats, leading to a silencing of the FMR1 gene and resulting in cognitive impairment, behavioral issues, and physical features such as an elongated face and large ears.

Lynch syndrome, also known as hereditary nonpolyposis colorectal cancer (HNPCC), is associated with mutations in mismatch repair genes but is not a trinucleotide repeat disorder. Duchenne muscular dystrophy is caused by mutations in the dystrophin gene and does not involve repeat expansions. Huntington disease involves an expanded CAG repeat in the HTT gene, which is distinct from the CGG repeat that characterizes Fragile X syndrome.