A pedigree chart is a diagram that shows the occurrence and appearance or phenotypes of a particular gene or organism and its ancestors from one generation to the next, most commonly humans, show dogs, and racehorses.
An important tool a geneticist uses to trace the inheritance of traits is a pedigree chart, for example, you can use a pedigree chart to track an inherited trait through several generations of a family. It is a family history and details about an earlier generation that may be uncertain as memories fade.
Elements of Pedigree chart
Pedigrees use a standardized set of symbols
- Squares represent males
- Circles represent females.
- If the sex of the person is unknown a diamond is used. Someone with the phenotype in question is represented by a filled-in (darker) symbol.
- Heterozygotes, when identifiable, are indicated by a shaded dot inside a symbol or a half-filled symbol.
- Relationships in a pedigree are shown as a series of lines.
- Parents are connected by a horizontal line and a vertical line leads to their offspring.
- The offspring are connected by a horizontal sibship line and listed in birth order from left to right.
- If the offspring are twins then they will be connected by a triangle. If an offspring dies then its symbol will be crossed by a line.
- If the offspring is stillborn or aborted it is represented by a small triangle.
Pedigree chart examples