The gene that causes Fragile X is called the FMR1 gene, which stands for Fragile X mental retardation gene. Though the term “mental retardation” has given way in recent years to the more generally accepted term of “intellectual disability”. Today, we simply refer to the “FMR1 gene” or the “Fragile X gene.”
The FMR1 gene is located on the X chromosome. We all have 46 chromosomes in all of our cells, 44 of which are numbered 1-22 in pairs. Then females have two X chromosomes and males have one X and one Y chromosome. Each chromosome has two arms, one called the “p” arm (the short arm) and one called the “q” arm (the long arm).
There are many genes on each chromosome, like houses on a street. Each gene is given an address, depending on where it lies on the chromosome. The address of the FMR1 gene is Xq27.3
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