Inheritance of Traits: Pedigrees and Genetic Disorders

1. Inheritance of Traits: Pedigrees and Genetic Disorders

2. Pedigree definition • Pedigree: a family history that shows how a trait is inherited over several generations • Pedigrees are usually used when parents want to know if they are carriers of a particular disorder

3. Making a Pedigree Filled in symbols indicate individual is affected with a disorder • Female • Male • Married Couple • Siblings

4. Example of a Pedigree Grandparents Grandparents Parents Aunts, Uncles Aunts, Uncles Brother You Do any disorders run in this family??

5. Interpreting a Pedigree • What can you tell from a pedigree? • Whether a family has an autosomal or sex-linked disease or disorder • Autosomal disorder: appears in both sexes equally • Sex-linked disorder: allele is located only on the X or Y chromosome. Most sex-linked genes are on the X chromosome and are recessive • So who would have an X-linked disorder more often, boys or girls? • Whether a disorder is dominant or recessive

6. Is this disorder 1) autosomal or sex linked, 2) dominant or recessive? Grandparents Grandparents Parents Aunts, Uncles Aunts, Uncles Sex Linked! (in this case allele is recessive and located on the X chromosome) Brother You

7. Is this disorder 1) autosomal or sex linked, 2) dominant or recessive? Grandparents Grandparents Parents Aunts, Uncles Aunts, Uncles Autosomal dominant! Brother You

8. Is this disorder 1) autosomal or sex linked, 2) dominant or recessive? Grandparents Grandparents Parents Aunts, Uncles Aunts, Uncles Autosomal recessive! Brother You

9. Common Genetic Disorders • Color blindness • Sickle cell anemia • Cystic Fibrosis • Hemophilia • Huntington’s Disease For more info, go to: http://www.ncbi.nlm.nih.gov/pubmedhealth/

10. Color Blindness • Deficiency to percieve colors • Problem with color-sensing pigments in certain nerve cells of the eye • About 1 in 10 men have some form of color blindness. • Sex-linked disorder

11. Sickle Cell Anemia • Disorder where abnormal hemoglobin (a protein inside red blood cells) is produced and warps red blood cells • Sickle cells deliver less oxygen to body’s tissues and can get stuck in small blood vessels • Recessive trait, tends to be seen in people of African or Mediterranean descent

12. Cystic Fibrosis • Recessive, autosomal disease • Life threatening, causes thick mucus to build up in various areas of the body (lungs, digestive tract, etc). • Tends to run in Caucasians, of Northern/Central European descent (1 in 29 Americans carry the allele) • Average life span in US for people with CF is 37, death usually caused by lung complications

13. Hemophilia • Bleeding disorder, where it takes a long time for blood to clot (body lacks proteins involved in clotting) • Sex-linked (carried on the X chromosome) • Treatment involves injection with missing clotting protein

14. Huntington’s Disease • Autosomal, dominant • Deterioration of brain tissue, usually begins between age 30 and 40. • No cure, but have medications to cope with symptoms • People usually die 15-20 years after onset of degeneration