X-linked recessive inheritance

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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). Females with one copy of the mutated gene are carriers. X-linked inheritance means that the gene causing the trait or the disorder is located on the X chromosome. Females have two X chromosomes while males have one X and one Y chromosome. Expression of X-linked conditions in female carriers can vary greatly due to random X-chromosome inactivation (Lyonization) within each cell. Differences in X-chromosome inactivation (known as skewed X-inactivation) occurs due to some cells expressing one X allele and some the other. Decades of research has shown that the notions "X-linked dominant" and "X-linked recessive" oversimplify the situation and it has been recommended...

Read on Wikipedia · Image File:Autosomal recessive - en.svg: Domaina, Kashmiri and SUM1 Derivative work: SUM1, CC BY-SA 4.0