Add people one at a time, connect them as parents and children, and see which inheritance patterns fit: autosomal recessive, X-linked, and more.
This tool takes a pedigree (a family tree showing who has a trait and who does not) and checks it against six standard inheritance patterns. For each pattern, it reports whether the pedigree is consistent with that pattern, ruled out by it, or ambiguous given the data you entered.
A pedigree chart in genetics is a diagram that tracks a trait through multiple generations of a family. Squares represent males, circles represent females. Filled shapes mean the person expresses the trait; open shapes mean they do not. Horizontal lines connect mating pairs, and vertical lines drop down to their children. The chart is read from top to bottom, with the oldest known generation at the top. Geneticists use these charts to work out how a trait is passed down before any DNA testing happens.
There are six common Mendelian inheritance patterns, and each leaves a distinct signature on a pedigree. Autosomal dominant traits appear in every generation. An affected person usually has at least one affected parent, and males and females show the trait at similar rates. Autosomal recessive traits can skip generations. Two unaffected parents can have an affected child if both carry one copy of the recessive allele.
Sex-linked patterns break the equal-rates rule. In X-linked recessive inheritance, males are affected far more often than females, and affected fathers never pass the trait to their sons (since sons inherit the Y chromosome, not the X). X-linked dominant inheritance is less common. An affected male passes the trait to all his daughters and none of his sons. Y-linked inheritance follows a strict father-to-son line with no females affected. Mitochondrial inheritance passes only through mothers. An affected mother transmits the trait to all her children, while an affected father transmits it to none.
The tool checks each of these rules against the relationships in your pedigree. If an affected father has an affected son, that rules out X-linked recessive (which cannot pass from father to son) but is consistent with autosomal dominant, autosomal recessive, Y-linked, and X-linked dominant. If an affected female has both an affected son and an unaffected son, X-linked dominant is ruled out (an affected mother would pass an X-linked dominant allele to all sons). The output is a list of which patterns survive this filtering.
A pedigree can only show which patterns are consistent and which are ruled out. It cannot prove which pattern is correct. Small families are often ambiguous because there are not enough affected individuals to distinguish between possibilities. A family with a single affected person is consistent with nearly every inheritance mode. The tool also assumes standard Mendelian inheritance and does not model reduced penetrance, variable expressivity, or de novo mutations.
A pedigree chart is a family tree diagram that shows which members have a particular trait and which do not. Males are represented as squares and females as circles. Filled shapes indicate individuals who express the trait. Geneticists use pedigree charts to trace how a trait passes through generations and to infer the most likely inheritance pattern.
You test the pedigree against known inheritance rules. If affected fathers never pass the trait to their sons, X-linked recessive is likely. If the trait skips generations and two unaffected parents have an affected child, autosomal recessive is possible. The process is elimination: rule out patterns that contradict the data, and see what remains.
Yes. Traits that skip generations are usually recessive. A person can carry one copy of a recessive allele without showing the trait. If two carriers have a child, that child can inherit two copies and express the trait even though neither parent does. This is characteristic of autosomal recessive and X-linked recessive inheritance.
Affected individuals often appear only in a single generation, with unaffected parents. Both parents are typically carriers. Males and females are affected at roughly equal rates. The trait can disappear for one or more generations and then reappear when two carriers have children together.
Autosomal inheritance involves genes on chromosomes 1 through 22 and affects males and females at similar rates. Sex-linked inheritance involves genes on the X or Y chromosome and shows different rates in males and females. X-linked recessive traits, for example, appear much more often in males because males have only one X chromosome.