Fragile X Syndrome Characteristics
Fragile X Syndrome is a genetic condition that causes intellectual disability, behavioral and learning challenges, and various physical characteristics. FXS is caused by changes in the fragile X mental retardation 1 (FMR1) gene. The FMR1 gene makes a protein called fragile X mental retardation protein (FMRP). FMRP is needed for normal brain development. People who do not produce this protein have FXS.
The FMR1 gene is located on the X chromosome; we all have 46 chromosomes in all of our cells. Out of 46 chromosomes, 44 chromosomes are numbered 1-22 in pairs. 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 and each gene is given an address, the address of the FMR1 gene is Xq27.3. The physical characteristic of the FXS chromosome looks like the end part of the …show more content…
A CGG repeat in the FMR1 gene is a pattern of 30 to 1000 times. An individual can have a normal range, intermediate, permutation, or a full mutation of the FMR1 gene. Individuals with less than 45 CGG repeats have a normal FMR1 gene. Those with 45-54 CGG repeats have what is called an intermediate or grey zone allele, which does not cause FXS. Individuals with 55-200 CGG repeats have a permutation, which means they carry on unstable mutation of the gene that can expand in the future generations and cause FXS in their children or grandchildren. The permutation has no immediate and observable impact on a person’s appearance or health. Individuals with more than 200 CGG repeats, have the full mutation. Most full mutation expansion has some degree of methylation. In FXS the methylation turns off the FMR1 gene, so no FMRP is produced, this is what causes
The FMR1 gene is located on the X chromosome; we all have 46 chromosomes in all of our cells. Out of 46 chromosomes, 44 chromosomes are numbered 1-22 in pairs. 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 and each gene is given an address, the address of the FMR1 gene is Xq27.3. The physical characteristic of the FXS chromosome looks like the end part of the …show more content…
A CGG repeat in the FMR1 gene is a pattern of 30 to 1000 times. An individual can have a normal range, intermediate, permutation, or a full mutation of the FMR1 gene. Individuals with less than 45 CGG repeats have a normal FMR1 gene. Those with 45-54 CGG repeats have what is called an intermediate or grey zone allele, which does not cause FXS. Individuals with 55-200 CGG repeats have a permutation, which means they carry on unstable mutation of the gene that can expand in the future generations and cause FXS in their children or grandchildren. The permutation has no immediate and observable impact on a person’s appearance or health. Individuals with more than 200 CGG repeats, have the full mutation. Most full mutation expansion has some degree of methylation. In FXS the methylation turns off the FMR1 gene, so no FMRP is produced, this is what causes