Pedigrees Pedigree charts show a record of the family of an individual. It can be used to study the transmission of a hereditary condition (genetic disease). It is particularly useful when there are large families and a good family record over several generations. Used in humans & animals.

Pedigree Analysis Symbols are used to represent males, females etc. For traits of interest, symbols can be shaded to indicate individuals carrying the trait. Individuals are designated by their generation number and then their order number in that generation. Normal female Affected male Sex unknown Died in infancy Affected female Normal male Non- identical twins Identical twins Carrier (heterozygote) Generations I, II, III Children (in birth order) 1, 2, 3

Pedigree Charts:

Pedigree Chart Symbols Males, Females, married, children, siblings, affected, normal Carrier (heterozygote)

Inheritance of Dominant Traits In the inheritance of autosomal dominant traits, each affected individual will have at least one parent who is also affected. If large number sof families are examined equal numbers of males and females are affected. Inheritance of the rare trait woolly hair in humans follows this pattern. In the 1st generation, female I-2 is heterozygous for a woolly hair allele. Half of her offspring are also heterozygous for the woolly hair allele, where t is expressed. The the rest (II-5, II-6, II-7) are homozygous recessive and have normal hair.

Inheritance of Recessive Traits The pedigree for albinism (lack of pigment in the hair, skin and eyes) is inherited as an autosomal recessive trait. The trait is not sex linked and is shown by both males and females. The affected female in the third generation has phenotypically normal parents. All generation II offspring are carriers for the albino allele. III-2 is an albino girl whose paternal grandmother and maternal grandfather are also albinos. All her other relatives are phenotypically normal.

Is this a recessive or dominant disease?

Sex Linked Hemophilia In the Royal Family