Presentation Transcript

1. Codominant vs Incomplete Dominant- What’s the difference?

2. Beyond Dominant and Recessive • Incomplete Dominance One allele is not completely dominant over the other – something in the middle is expressed Ex. Red and White Snapdragons Result can be heterozygous (Rr) or two separate dominant alleles (RW) each resulting in a mixture of both alleles

3. Another way that incomplete dominance can be expressed • Red= RR • White= WW • RW= pink- each allele is equally expressed to result in a blended product

4. One way to express incomplete dominance • RR (Red) X rr (White)= (Rr)Pink • Rr- results in a blended result of PINK

5. Incomplete Dominance Practice • In certain cats, tail length is determined by a gene that demonstrates incomplete dominance. The allele that causes a long tail (T) is not completely dominant over the allele that causes no tail (t). If a cat is heterozygous forthis trait (Tt), then the cat will have a short tail. What is the probability that the offspring will be manx cats (no tail) if a short – tailed cat is bred with a manx cat (no tail)?

6. Incomplete Dominance Practice • Incomplete dominance is seen in snapdragons. The allele that causes red flowers (F) is not completely dominant over the allele that causes white flowers (f). When a plant is heterozygous for the trait of flower color (Ff), pink flowers result. Cross two pink snapdragons, and provide the genotype and phenotype of all offspring.

7. Beyond Dominant and Recessive • Codominance Both alleles are expressed in the phenotype Ex. Cow Hair Color RR – Red WW – White RW – Roan (Red & White) Practice Codominance/Incomplete Dominance #1-4

8. Beyond Dominant and Recessive • Multiple Alleles Genes have more then two alleles Ex. Blood Type Type A blood- AA or AO alleles A is dominant to O Type B blood- BB or BO alleles B is dominant to O Type AB- codominant- A and B alleles A nor B is dominant so both are expressed on organisms RBC Type O- recessive- OO alleles Both alleles must be recessive in order to have type O.

9. More on blood types….. • The blood type determines what antibodies are located within the blood. Type A blood has type B antibodies. If type B blood is put into their bodies, their immune system reacts as if it were a foreign invader, the antibodies clump the blood - can cause death. • Type AB blood has no antibodies, any blood can be donated to them - they are called the "universal acceptors" • Type O blood has no surface markers on it, antibodies in the blood do not react to type O blood, they are called the "universal donors"

11. Co-dominance Practice • In humans, blood types A and B are equally dominant (codominant). Both types are dominant to type O. A man with type AB blood marries a woman with type O blood. Give the genotypes and phenotypes of all possible offspring.

12. Co-dominance Practice • If a man with blood type A, one of whose parents had blood type O, marries a woman with blood type O, what percentage of their offspring would have blood type OO?

13. Polygenic Traits • Traits that are controlled by the interaction of several genes. • Example: • Reddish brown eyes in varying degrees found in fruit flies is controlled by 3 genes • Human skin color is controlled by 4 different genes which result in a variety of skin color.

14. Sex-linked Genetics Ex. Colorblindness

15. Sex Chromosomes- last pair (23rd) in a karyotype MALE KARYOTYPE FEMALE KARYOTYPE

16. Sex Chromosomes- last pair (23rd) in a karyotype • Male – XY and Females – XX • The 23rd pair of chromosomes will determine the gender of an individual • Very few genes are located on the Y chromosome……Most are located on the X • Sex linked alleles will ALWAYS be tracked on the X chromosome ONLY when we conduct practice genetic problems

17. Sex-Linked Genes • Ex. Colorblindness is carried on the sex-chromosomes • It is a recessive trait – Xc How many genes do females need to express the trait (colorblindness)? 2 Xc Xc How many genes do males need to express the trait (colorblindness)? 1 XcY

18. Sex-Linked Punnett Square • Let C = Normal Vision and c = Colorblind • Cross: Normal Male ( ) x Carrier Female ( )

19. Sex-Linked Punnett Square C • Let C = Normal Vision and c = Colorblind • XY x X X = Normal Male x Carrier Female XY X X C C c 1st put male genotype on the top of the table & female genotype on the left side C C c

20. Sex-Linked Punnett Square C • C – Normal Vision and c - Colorblind • XY x X X - Normal Male x Carrier Female XY X X C C c C 2nd, cross them X X X Y X X X Y C C C C C c c c

21. Sex-Linked Punnett Square C • C – Normal Vision and c - Colorblind XY x X X -Normal Male x Carrier Female XY X X 3rd, list the sex and appearance of each possible offspring C C c C Offsprings: 1 Normal Female 1 Normal (Carrier) Female 1 Normal Male 1 Colorblind Male X X X Y X X X Y C C C C C c c c

22. Sex-linked Practice • Hemophilia is a disease caused by a gene found on the X chromosome. Therefore, it is referred to as a sex – linked disease. The recessive allele causes the disease. A normal man marries a woman that is heterozygous for the trait. Give the genotypes and phenotypes of all possible offspring. Will any of their children have the disease?

23. PRACTICE and HW • Complete problems 1-3 on the sex linked genetic practice problems sheet NOW! • Complete the remaining 3 Co-dominant and Incomplete dominant practice problems and Sex Linked practice problems # 4-8 from today’s class for HW