Pedigree Charts/Single Gene Inherited Disorders

Wild-Type Trait

prevalent trait in nature not necessarily specified by dominant alleles

Recessive Disorders

* most human genetic disorders are recessive
* most individuals are born with healthy heterozygous parents (carriers)
* lethal disorders can be hidden via heterozygotes

Dominant Disorders

* dominant lethal disorders are less common than recessive ones
* lethal disorders are caused by mutations that generally kill sperm/egg/embryo
* generally don’t live along enough to reproduce

Pedigree

chart used to reveal patterns of inheritance

Questions to ask every pedigree

1. Can the trait skip generations?
2. How many people have the trait?
3. Do equal amounts of males and females have it? (doesn’t need to be perfectly equal)

Autosomal Recessive Inheritance

* skips generations
* not many have it
* equal number of males and female

Autosomal Dominant Inheritance

* doesn’t skip generations
* lots have it
* equal numbers of males and females have it

X-linked (sex linked)

* unequal number of males and females have it
* recessive if carriers exist or if it skips generations