1. Genetics

2. Dihybrid Crosses Dihybrid crosses are the comparison of genetic makeup for two characteristics. EX: color and shape. Mendel used dihybrid crosses to determine the principle of independent assortment: this principle tells us that genes for two characteristics can be passed on independently of each other.

3. Dihybrid Punnett Squares 1.One capital/lowercase letter is assigned to one of the traits and a different capital/lowercase letter is assigned to the other trait. 2.Find the possible combinations that each parents’ gamete could contain. 3.Fill in the Punnett Square and work as you normally would.

4. Dihybrid Punnet Squares: EX Peas can be yellow or green. –Yellow is dominant Y and green is recessive y. Peas can be round or wrinkled. –Smooth is dominant R and wrinkled is recessive r. Ex: mom is RrYy and dad is RrYy (both display round and yellow characteristics)

5. Dihybrid Punnett square: Mom  Dad RYrYRyry RYRRYYRrYYRRYyRrYy rYRrYYrrYYRrYyrrYy RyRRYyRrYyRRyyRryy ryRrYyrrYyRryyrryy

6. Polygenic Traits Polygenic traits are traits that are determined by the combined effects of more then one gene. They do not follow the normal inheritance laws and for some the Punett Square is not effective for predicting inheritance.

7. Codominance Genetic traits that are codominant have no recessive trait. This means that both the capital form and lowercase form of the gene are FULLY expressed. Example: HH, Hh, hh from “making baby” lab. ABO blood type.

8. Codominance: Determining the offspring Use all capital letters, choose a letter and then give it a superscript. Ex, the gene C for flower color white and yellow is codominant. C w = white and C y = yellow. You can still use the traditional punnet square, however, the heterozygous individual will be white with large yellow spots.

9. Codominance C w C w = white C y C y = yellow C w C y = white with yellow spots CwCw CwCw CyCy C w C y CyCy

10. Incomplete dominance The dominant gene cannot completely “beat” the recessive gene. Results in a blending of the dominant and recessive trait. Ex: sickle cell disease. Individuals with SS = normal blood cell shape, ss= severe sickle cell blood cell shape, Ss= a minor change in blood cell shape.

11. Incomplete dominance: determining the offspring Assign a capital letter to the dominant trait and a lowercase letter to the recessive trait. Complete the punnett square in the exact wayyou have learned. The heterzygous individuals will display a trait that is some of the dominant form mixed with some of the recessive form. (neither is completely expressed)

12. Incomplete dominance RR = red petal plant rr= white petal plant Rr=pink petal plant RR R RR r Rr

13. Multiple Alleles Traits controlled by more then two alleles (gene types) are said to be controlled by multiple alleles. Even if there are 100 alleles, you can only carry two of them! Example: ABO blood type.

14. ABO blood type: determining the offspring A, and B are dominant while O is the recessive form of the red blood cell proteins. AA and AO are the “A blood type” BB and BO are the “B blood type” AB is the “AB blood type” where both the A proteins and the B proteins are expressed. The ABO blood types are an example of codominance and multiple alleles. A and B are two different dominant alleles while O is the recessive allele.

15. Multiple Alleles A=dominant A blood type B=dominant B blood type O= recessive blood type AA B AB OAO