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Trisomy X, also known as triple X syndrome and characterized by the karyotype [note 1] 47,XXX, is a chromosome disorder in which a female has an extra copy of the X chromosome. It is relatively common and occurs in 1 in 1,000 females, but is rarely diagnosed; fewer than 10% of those with the condition know they have it.
The following is a list of genetic disorders and if known, type of mutation and for the chromosome involved. Although the parlance "disease-causing gene" is common, it is the occurrence of an abnormality in the parents that causes the impairment to develop within the child. There are over 6,000 known genetic disorders in humans.
Fragile X syndrome is caused by expansion of CGG repeats in the FMR1 gene. In males without fragile X syndrome, the CGG repeat number ranges from 53 to 200 while those affected have greater than 200 repeats of this trinucleotide sequence located at the end of the X chromosome on band Xq28.3.1. [36]
An X-linked genetic disease is a disease inherited through a genetic defect on the X chromosome. In human cells, there is a pair of non-matching sex chromosomes , labelled X and Y. Females carry two X chromosomes, whereas males have one X and one Y chromosome .
Females have two X chromosomes while males have one X and one Y chromosome. Carrier females who have only one copy of the mutation do not usually express the phenotype, although differences in X-chromosome inactivation (known as skewed X-inactivation) can lead to varying degrees of clinical expression in carrier females, since some cells will ...
In genetics, trinucleotide repeat disorders, a subset of microsatellite expansion diseases (also known as repeat expansion disorders), are a set of over 30 genetic disorders caused by trinucleotide repeat expansion, a kind of mutation in which repeats of three nucleotides (trinucleotide repeats) increase in copy numbers until they cross a threshold above which they cause developmental ...
Triploidy is caused by an extra set of chromosomes. [citation needed] Triploidy can result from either two sperm fertilizing one egg (60%) or from one sperm fertilizing an egg with two copies of every chromosome (40%). [2] These are otherwise known as diandric fertilization and digynic fertilization.
A karyotype of an individual with trisomy 21, showing three copies of chromosome 21.. An abnormal number of chromosomes is known as aneuploidy, and occurs when an individual is either missing a chromosome from a pair (resulting in monosomy) or has more than two chromosomes of a pair (trisomy, tetrasomy, etc.).