Which statement is true about Fragile X Syndrome?

Which statement is true about Fragile X Syndrome?

• A. It is caused by a mutation on the X chromosome and more common in boys
• B. It is caused by a mutation on the Y chromosome
• C. It is an autoimmune condition
• D. It is due to vitamin deficiency

Answer: (A)

Fragile X Syndrome is caused by a mutation in the FMR1 gene on the X chromosome, typically a CGG trinucleotide repeat expansion that silences the gene and reduces the production of the FMRP protein needed for normal neural development. Because the gene is on the X chromosome, inheritance is X-linked. Males are more frequently and more severely affected because they have only one X chromosome, so a single mutated copy usually leads to the full expression of the condition. Females have two X chromosomes, and random X-inactivation can spare some cells, often resulting in milder symptoms or even normal function in many cases. The other statements aren’t correct because the mutation isn’t on the Y chromosome, it isn’t an autoimmune condition, and it isn’t caused by a vitamin deficiency.

Fragile X Syndrome is caused by a mutation in the FMR1 gene on the X chromosome, typically a CGG trinucleotide repeat expansion that silences the gene and reduces the production of the FMRP protein needed for normal neural development. Because the gene is on the X chromosome, inheritance is X-linked. Males are more frequently and more severely affected because they have only one X chromosome, so a single mutated copy usually leads to the full expression of the condition. Females have two X chromosomes, and random X-inactivation can spare some cells, often resulting in milder symptoms or even normal function in many cases. The other statements aren’t correct because the mutation isn’t on the Y chromosome, it isn’t an autoimmune condition, and it isn’t caused by a vitamin deficiency.