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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.
In an X-linked recessive disorder, males are more likely to be affected than females. Affected sons typically have unaffected mothers. The father also must be affected for the daughter to be affected, and the mother must be affected or a carrier for the daughter to be affected. The disorder is also never passed from father to son.
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 ...
Four different traits can be identified by pedigree chart analysis: autosomal dominant, autosomal recessive, x-linked, or y-linked. Partial penetrance can be shown and calculated from pedigrees. Penetrance is the percentage expressed frequency with which individuals of a given genotype manifest at least some degree of a specific mutant ...
[13] [11] [14] In X-linked recessive conditions, males are typically affected more commonly because they are hemizygous, with only one X chromosome. In females, the presence of a second X chromosome will prevent the condition from appearing. Females are therefore carriers of the condition and can pass the trait on to their sons. [13] [11] [14]
Sex linked diseases are passed down through families through one of the X or Y chromosomes. Since usually men inherit Y chromosomes, they are the only ones to inherit Y-linked traits. Men and women can get the X-linked ones since both inherit X chromosomes. [21] An allele is either said to be dominant or recessive. Dominant inheritance occurs ...
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An example pedigree chart of an autosomal dominant disorder An example pedigree chart of an autosomal recessive disorder An example pedigree chart of a sex-linked disorder (The gene is on the X chromosome.) The description of a mode of biological inheritance consists of three main categories: 1. Number of involved loci