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In medicine, X-linked dominant inheritance indicates that a gene responsible for a genetic disorder is located on the X chromosome, and only one copy of the allele is sufficient to cause the disorder when inherited from a parent who has the disorder. In this case, someone who expresses an X-linked dominant allele will exhibit the disorder and ...
Illustration of some X-linked heredity outcomes (A) the affected father has one X-linked dominant allele, the mother is homozygous for the recessive allele: only daughters (all) will be affected. (B) the affected mother is heterozygous with one copy of the X-linked dominant allele: both daughters and sons will have 50% probability to be affected.
Pseudodominance is the situation in which the inheritance of a recessive trait mimics a dominant pattern. [1]Normally, two recessive alleles need to be inherited (one from each parent) for the recessive trait to be expressed but recessive merely means that the trait is only expressed in the absence of the dominant alleles.
Indeed, over 20% of X-linked genes are expressed from the inactive X chromosome and they contribute to sexually dimorphic traits. The X chromosome makes a very small percentage of the total human genome and the epigenetics of this chromosome is a major contributor to certain diseases.
X-linked dominant traits can affect females as much as males. X-linked dominant inheritance occurs less frequently. Only one copy of the mutated alleles on the X chromosomes is sufficient to cause the disorder when inherited from an affected parent. Unlike in X-linked recessive inheritance, X-linked dominant traits can affect females as much as ...
X-linked recessive inheritance. X-linked recessive inheritance is a mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be always expressed in males (who are necessarily hemizygous for the gene mutation because they have one X and one Y chromosome) and in females who are homozygous for the gene mutation, see zygosity.
Choroideremia (/ k ɒ ˌ r ɔɪ d ɪ ˈ r iː m i ə /; CHM) is a rare, X-linked recessive form of hereditary retinal degeneration that affects roughly 1 in 50,000 males. The disease causes a gradual loss of vision, starting with childhood night blindness, followed by peripheral vision loss and progressing to loss of central vision later in life.
As a result, X-linked dominant disorders usually show higher expressivity in males than females. [ citation needed ] As the X chromosome is one of the sex chromosomes (the other being the Y chromosome ), X-linked inheritance is determined by the sex of the parent carrying a specific gene and can often seem complex.