1. Mendelian Inheritance of Human Traits

2. Simple Recessive Heredity
When a person gets two recessive alleles.
Simple Recessive Genetic Disorder
Cystic Fibrosis (thick accumulation of mucus in lungs and digestive tract)
Tay-Sachs (disease of the central nervous system)
Phenylketonuria-PKU (results in damage to central nervous system)

3. Simple Dominant Heredity
When a person gets at least one dominant allele.
Simple Dominant Traits
Tongue Rolling
Huntingtons Disease (results in a breakdown of certain areas of the brain)

4. Complex Patterns of Inheritance

5. Incomplete Dominance
a heterozygote has a different phenotype as the two homozygotes
Example-Red flowers are RR, white are WW, the heterozygous condition, RW produces pink flowers

6. Codominant
in a heterozygote individual both phenotypes are expressed equally
Example – cross a black chicken (BB) and a white chicken (WW) the heterozygote wouldn’t be grey, the chicken has both black and white feathers.

7. Codominant, cont.
Example:  Blood type gene has three different alleles (each person has two of the three possibilities)
Type A allele is dominant and produces A type protein on red blood cells
Type B allele is dominant and produces B type protein on red blood cells
Type O allele is recessive (defective) allele and produces no protein on red blood cells

8. Blood Type Genotype Phenotype AA or AO A BB or BO B AB only AB OO only

9. Blood Type

10. Polygenic Inheritance
- the inheritance pattern of a trait that is controlled by two or more genes.
Examples in humans include
hair color (AABBCC)
eye color
skin color

11. Sex-linked Traits
There are 22 pairs of chromosomes in your body that are called autosomes.
The other pair are called sex chromosomes. They are called “X” and “Y”.
Female genotype = XX
Male genotype = XY

12. Sex-Linked Traits, cont.
Some human traits are determined by genes carried on the sex chromosomes, most of these genes are on the X chromosome.
Color blindness and hemophilia are examples of sex-linked traits.

13. Environmental Influences
There are many, many environmental factors that affect the way our genes are expressed.

14. Karyotype A karyotype is a chart of chromosome pairs.
This technique is used to look at the chromosomes and tell if the individual has the normal number and type.

15. Pedigree Charts

16. Pedigree Charts
A Pedigree chart is a graphic representation of genetic inheritance.
kind of like a family tree

17. Pedigree Charts, cont.
When you carefully make a pedigree chart you should be able to tell which individuals are possible carriers and the probability that future offspring will express the trait shown.