Consanguinity

Consanguinity is a biological relationship between people who share an ancestor. The term is especially used in discussions of marriage, inheritance, and the increased chance that relatives carry the same inherited genetic variants.

Identity by descent: Genetic copies inherited from the same ancestral copy rather than matching by chance. It explains how relatives can inherit the same variant from a shared ancestor.
Genetic counseling: A health service that helps people understand inherited conditions, genetic tests, and reproductive options. Counselors can assess family history and discuss risks associated with related parents.
Affinity (law): A relationship created through marriage rather than shared biological ancestry. Affinity can connect families socially or legally without creating consanguinity.
Homozygosity: The possession of two identical alleles at a genetic locus. Increased homozygosity can expose recessive variants inherited from shared ancestors.
Coefficient of relationship: A measure of the expected proportion of genetic material shared by descent between two individuals. It quantifies genetic relatedness between prospective parents or family members.
Carrier screening: Testing people without symptoms to identify variants associated with inherited conditions in offspring. Screening can identify shared recessive variants in couples with common ancestry.
Unrelatedness: The absence of a known close genealogical relationship between individuals. It contrasts shared ancestry, though unrelated people may still carry the same common variant.
Congenital disorder: A structural or functional condition present at birth, arising from genetic or environmental causes. Some inherited congenital disorders are more frequent when parents share ancestry.
Autozygosity: The state of carrying two copies of a genetic segment that descend from the same ancestral copy. Shared ancestry can make a descendant's matching chromosome segments autozygous.
Founder effect: A change in genetic variation that occurs when a population is established by a small number of ancestors. Founder populations may combine shared ancestry with elevated frequencies of particular variants.

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