• A pedigree is a chart of the genetic history of a family over several generations.

• Males are represented as squares.

• Females are represented as circles.

• Shaded symbols signify that the individual is affected by the condition.

• Unshaded shapes signify that the individual is unaffected by the condition.

• A horizontal line between man and woman represents mating and resulting children are shown as offshoots to this line.

• Generations are labeled with Roman numerals.

• Individuals are ordered best on age. Oldest to the left, and youngest to the right.

Autosomal Dominant -

• If both parents are affected and an offspring is unaffected, the trait must be autosomal dominant (parents are both heterozygous).

• All affected individuals for autosomal dominant must have at least one affected parent.

• If both parents are unaffected for autosomal dominant traits, all offspring must be unaffected (homozygous recessive).

Autosomal Recessive -

• If both parents are unaffected and an offspring is affected in autosomal recessive, the trait must be recessive (parents are heterozygous carriers).

• If both parents show a trait in autosomal recessive, all offspring must also exhibit the trait (homozygous recessive).

X-Linked Recessive -

• If a female shows a trait in X-linked recessive, so too must all sons as well as her father.

• An unaffected mother in x-linked recessive genes can have affected sons if she is a carrier (heterozygous).

• X-linked recessive traits tend to be more common in males.