Autosomal recessive trait
In genetics, autosomal recessive is a mode of inheritance of genetic traits located on the autosomes (i.e. the 22 non-sex determining chromosomes).
In opposition to autosomal dominant trait, a recessive trait only becomes phenotypically apparent when two copies of a gene (two alleles) are present, i.e. the propositus is homozygous for the trait.
Recessive genetic disorders occur when both parents are carriers and each contribute an allele to the embryo. As both parents are heterozygous for the disorder, the chance of two disease alleles landing in one of their offspring is 25% (in autosomal dominant traits this is higher). 50% of the children (or 2/3 of the remaining ones) are carriers. When one of the parents is homozygous, the trait will only show in his/her offspring if the other parent is also a carrier. In that case, the chance of disease in the offspring is 50%.
Other forms of inheritance are autosomal dominant, X-linked and mitochondrial.
Examples of recessive disorders:
See also
