How can human traits be traced through generations? Pedigree How can human traits be traced through generations?

Pedigree Chart which shows the relationships within a family Deals with the inheritance of a single gene Pedigrees show how a trait is transmitted through three generations of a family

Pedigree In a sex linked pedigree men will have the disease and women will mostly be carriers of the disease.

Pedigree Male Female

Pedigree Male Carrier Female Carrier

Pedigree Male with expressed trait Female with expressed trait

Pedigree A horizontal line connecting male and female represents marriage

Pedigree Vertical line and a bracket connect the parents to their children

Types of Inheritance Autosomal Recessive Inheritance Autosomal Dominant Inheritance Sex-Linked Recessive Inheritance

Autosomal Recessive Inheritance Expression of disease only in homozygous recessive state (skips generations Carriers usually have no symptoms Both males and females are affected Certain disorders can occur more frequently in different ethnic backgrounds Examples: Albinism, Cystic Fibrosis & PKU

Autosomal Recessive Pedigree

Albinism

Autosomal Dominant Inheritance Dominant gene mutation Expression of disease in heterozygous state Seen in all generations (no skipping) Variable expressivity Example: Neurofibromatosis & Huntington’s

Autosomal Dominant Pedigree

Neurofibromatosis

males affected, females usually unaffected carriers X-Linked Recessive Inheritnce males affected, females usually unaffected carriers affected males do not have affected children Example: Color blindness

Color blindness