1. Understanding Inheritance Main Idea: The interactions among alleles, genes, and the environment determine an organism’s traits.

2. Modeling Inheritance A Punnett square is a model used to predict possible genotypes and phenotypes of offspring. Bb bb B B

3. Pedigrees A pedigree shows genetic traits that were inherited by members of a family tree. A pedigree usually only indicates the phenotype of individuals. The genotypes of the individuals may not be known but can often be determined.

4. Pedigrees, continued Besides tracking common inherited traits, pedigrees are important tools to track complex patterns of inheritance and genetic disorders in families. https://youtu.be/Wuk0W10EveU

5. Pedigree example Squares represent males. Circles represent females. Connected line means relationship. Colored means has the trait. Semi-colored means person is a carrier of the trait. Blank does not have the trait.

6. Complex patterns of Inheritance Not all allele pairs have a dominant- recessive interaction. Some have incomplete dominance and codominance interactions.

7. Incomplete Dominance Sometimes traits appear to be blends of alleles. Alleles show incomplete dominance when they produce a phenotype that is a blend of the parents phenotypes.

8. Codominance The human blood type AB is an example of another type of interaction between two alleles. When both alleles can be observed in a phenotype, this type of interaction is called codominance. If an individual inherits the B allele from one parent and an A allele from the other parent, he or she will have type AB blood.

9. Multiple Alleles The human ABO blood type is an example of a trait that is determined by multiple alleles. Even though there are multiple alleles, a person can only inherit two of these alleles – one from each parent. https://youtu.be/9O5JQqlngFY

10. Sex-Linked Inheritance Traits may be sex-specific. Color blindness is an example of a sex- linked trait. This is due to the fact that the Y chromosome is shorter than the X chromosome. Therefore each of those genes has only one allele (on the X chromosome). https://youtu.be/h2xufrHWG3E

11. Polygenic Inheritance Traits may be influenced by more than one gene. Height, weight, and skin color are traits that are polygenic.

12. Human Genetic Disorders An inherited mutation can result in a genetic disorder, which can result in health problems. Some genetic disorders include Huntington’s disease, sickle-cell, hemophelia, and Down syndrome.

13. Genes and the Environment Traits might be influenced by the environment. Many genes affect a person’s chances of having heart disease. However, poor diet and exercise can influence whether heart disease will develop.

14. Genes and the environment These hydrangea plants are genetically identical. The acidic conditions of the soil in which they grow determines flower color – more acidic produces blue flowers.