Human Genetics: Pedigree

Genes are pieces of DNA that code for a trait.

Example: Codes for hair, eye, skin color

Genes are passed from parents to offspring. This is called heredity.

Heredity can be studied using a pedigree chart Heredity can be studied using a pedigree chart. This shows your family history for a particular trait.

Pedigree: the record of descent of an animal

Males are always represented with a box; females with a circle.

Those who carry the trait have the symbol filled in Those who carry the trait have the symbol filled in. Those who carry it (heterozygous) have half the box filled in.

Shaded in- Affected Left blank- Non Affected

Twins/Triplets

DD D D dd d d Dd D d Dominant, Dominant Recessive, Recessive

Example: Make a pedigree for a father with black hair, a wife without, and three children: one boy, and two girls. All children have black hair

Dominant traits show up in every generation, whereas recessive traits do not.

Sex-linked traits deal with one’s gender Sex-linked traits deal with one’s gender. These are most-often found in males.

Is the trait in this pedigree dominant or recessive? Sex-linked or not?

Step One: Create 3 Generations II.------------------------------------------------ III.-----------------------------------------------

Step 2: Start with 3rd Gen first. II.------------------------------------------------ III.--------------------------------------------- You, siblings, step-siblings, cousins

Step 3- Add 2nd Gen I. ------------------------------------------------ II.------------------------------------------------ Parents, step-parents, aunts, uncles III.--------------------------------------------- You, siblings, step-siblings, cousins

Step 4- Add 1st Gen I. ------------------------------------------------ Grandparents II.------------------------------------------------ Parents, step-parents, aunts, uncles III.--------------------------------------------- You, siblings, step-siblings, cousins