1. Heredity and Genetics
Chapter 12.1

2. Heredity and Genetics Why is it important?
Inherited traits affect your appearance and health
Some traits are harmless
Some produce medical disorders

3. Heredity and Genetics Scientists study patterns of inheritance
Research treatments and cures for diseases
Pedigree = a diagram of genetic inheritance
Like a family tree with information about genes
○=female □=male ◨=heterozygous male ■= affected male
I ○ □
II □ ○ 1 2 1 2

4. Heredity and Genetics
Example Pedigree

5. Simple recessive heredity
You have to inherit one recessive allele from each parent to have the trait.
Most genetic disorders are caused by recessive alleles
Rare recessive alleles are sometimes more common in certain ethnic groups

6. Simple recessive heredity
Example pedigree with a recessive trait 6

7. Simple recessive heredity
Cystic fibrosis
1/20 white Americans carry recessive allele
Defective protein causes formation of thick mucus in lungs and digestive tract
Physical therapy, special diet and medication increase life expectancy

8. Simple recessive heredity
Tay-Sachs disease
Recessive allele common among Amish and Ashkenazi Jews from Eastern Europe
Absence of an enzyme that breaks down lipid in tissue of the brain and spinal cord
Build up of lipid causes deterioration of mental and physical abilities. There is no cure.

9. Simple recessive heredity
Phenylketonuria (PKU)
Most common in Norway and Sweden
Absence of an enzyme that breaks down phenylalanine to tyrosine, accumulation causes damage to the brain
Babies can be tested and given a special diet until brain completes development

10. Simple dominant heredity
Inherit one dominant allele from a parent to express trait
Tongue rolling T
Detached earlobe F
Hitchhiker’s thumb H
Widow’s peak W
pedigree

11. Simple dominant heredity
Example pedigree with dominant trait 11

12. Simple dominant heredity
Huntington’s disease
Rare dominant allele
Breakdown of brain cells
Onset at years old, after having children

13. Heredity and genetics
Table of genetic disorders

14. Heredity and genetics
Why is genetics important to couples considering having children? 14