Autosomal recessive inheritance

Autosomal recessive inheritance is a pattern in which a condition usually occurs when both copies of an autosomal gene are altered. People with one altered copy are often unaffected carriers.

Allele: One of two or more versions of a genetic sequence at a particular genomic location. Each parent passes one allele of the relevant autosomal gene to a child.
Autosome: A chromosome that is not one of the sex chromosomes. The inheritance pattern concerns genes on chromosomes other than the sex chromosomes.
Punnett square: A diagram used to enumerate possible offspring genotypes from parental alleles. It displays the one-in-four affected probability when both parents carry the same recessive variant.
Autosomal dominant inheritance: A pattern in which one altered copy of an autosomal gene is usually sufficient to cause a condition. Unlike recessive inheritance, one altered copy can be enough to produce the condition.
Homozygosity: The state of having identical alleles at a particular genetic locus. Two matching altered alleles can produce a recessive condition.
Genotype: The genetic constitution of an organism, or the allele combination at a particular locus. Recessive conditions depend on the allele combination at a gene.
Pedigree chart: A diagram representing family relationships and the inheritance of traits across generations. Family patterns can reveal unaffected carriers and affected relatives.
X-linked recessive inheritance: A pattern in which variants on the X chromosome cause conditions more often in people with one X chromosome. It involves a sex chromosome, so risks differ by sex and parental transmission.
Compound heterozygosity: The presence of two different disease-associated variants in the same gene, one on each chromosome copy. Different altered copies of one gene can together cause a recessive condition.
Phenotype: Observable characteristics of an organism, shaped by genes and environment. Inheritance describes genotypes, while diagnosis often rests on the resulting traits.

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