AIM: Non- Mendelian Genetics

1. Do Now :What is the probability that a heterozygous cross will produce homozygous recessive offspring? AIM: Non-Mendelian Genetics

2. Non-Mendelian Genetics • Some traits don’t follow the simple dominant/recessive rules that Mendel first applied to genetics. • Traits can be controlled by more than one gene. • Some alleles are neither dominant nor recessive.

3. Incomplete Dominance • One allele is not completely dominant over another. • The heterozygous phenotype is a blending of the two homozygous phenotypes. Example: four o’clock flowers • rr=red • ww=white • rw=pink (blending of the two alleles)

4. Codominance • Two alleles are both expressed as a dominant phenotype • Coat color in cows • RR: Red • WW: White • RW: Roan, white with red spots (NOT pink!)

5. Codominance More than two choices of alleles are present for a trait ABO blood type has three alleles ABO Blood types: If both A and B are present, type is AB Neither is recessive Individuals can be type A, B, AB, or O (recessive)

7. Blood transfusions – who can receive blood from whom? • The transfusion will work if a person who is going to receive blood has a blood group that doesn't have any antibodies against the donor blood's antigens.

8. People with blood group 0 are called "universal donors" and people with blood group AB are called "universal receivers."

9. Polygenic Inheritance When several genes affect a character, it is called a polygenic character. • eye color is affected by several genes. One gene controls the relative amount of greenness of the eye, and another gene controls brownness. (The recessive condition in both cases is blue eyes.) • Other genes also affect eye color. • Other examples of polygenic characters in humans are height and skin color. In fact, most characters are polygenic.

10. Genes Affected by the Environment • Phenotype can be affected by conditions in the environment, such asnutrients and temperature.

12. Sex-Linked Inheritance

13. Review • Males have an X and a Y chromosome • Females have two X chromosomes • These chromosomes determine sex, so genes located on these chromosomes are known as sex-linked genes.

14. The X chromosome is much larger than the Y, so it carries more genes than the Y chromosome. • Disorders that are sex-linked are much more common in males, because they would only need 1 recessive allele to have the trait; rather than the two recessive alleles the females need.

15. Hemophilia • Recessive trait • Disorder where individuals are missing the normal blood clotting protein. • Uncontrolled bleeds from minor cuts or bruises. • Female genotype: XhXh (with disease) • XHXh ( carrier) • Male genotype: XhY

16. Color blindness • Recessive • Inability to see certain colors • Female genotype: XbXb –colorblind • XbXB - carrier • Male genotype: XbY- colorblind

17. Genetics of Calico Cat • Calico is a coat color found in cats, which is caused by a SEX-LINKED, CODOMINANT allele. • B = BlackR = OrangeBR = Calico • The following genotypes are possible; • Female cats can be blackXBXB, orange XRXR, or calicoXBXRMale cats can be blackXBY or orange XRY

18. Show each of the crosses below and include the phenotypic ratios of the offspring. • 1. A black male crossed with an orange female •  2. An orange male crossed with a calico female

19. Practice for non-Mendelian Genetics A woman who is heterozygous for normal vision marries a man who is colorblind. What are the chances of them having a son or daughter who is colorblind? **NOTE: You have to use X’s and Y’s, and read the Punnett square separately for boys and girls!**

20. A woman who is homozygous for normal blood clotting marries a man who has hemophilia. What are the chances of them having a son or daughter with hemophilia?