2. GENETICS

3. Medelian Genetics Gregor Mendel 1800’s

5. Medelian Genetics all purple flowers result Pollen transferred from white flower to stigma of purple flower self-pollinate ?

6. F2 generation 3:1 75% purple-flower peas 25% white-flower peas Looking closer at Mendel’s work Parents 100% F1 generation (hybrids) 100% purple-flower peas X true-breeding purple-flower peas true-breeding white-flower peas self-pollinate

7. We use letters to represent the alleles or genes. P = purple p = white Purple is dominant over white. White is recessive. GenotypePhenotype PP Pp pp Purple White Homozygous dominant Heterozygous or hybrid Homozygous recessive

8. Predicting Inheritance Let’s cross a totally dominant tall plant (TT) with a short plant (tt). Each plant will give only one of its’ two genes to the offspring or F 1 generation. TT x tt TTtt

9. Predicting Inheritance Let’s cross a totally dominant tall plant (TT) with a short plant (tt). Each plant will give only one of its’ two genes to the offspring or F 1 generation. TT x tt TTtt Mendels’ “Law” of Segregation Each gene (allele) separates from the other so that the offspring get only one gene from each parent for a given trait.

10. Punnett Squares TtTtTt The genes from one parent go here. The genes from the other parent go here.

11. Punnett Squares TtTtTt

12. Punnett squares Pp x Pp Pp male / sperm P p female / eggs PP 75% 25% 3:1 25% 50% 25% 1:2:1 % genotype % phenotype PPPpPp PpPppp PpPp PpPp 1 st generation (hybrids) Aaaaah, phenotype & genotype can have different ratios

13. What if you didn’t know the genotype of an individual? TEST CROSS Let’s say Gray is dominant over white in mice. If we have a gray individual, how could we determine if it is homozygous or heterozygous gray?

14. Cross the gray mouse by a white mouse. What do you get? If you get 100% all gray, then the genotype must have been GG 1 white individual, then the genotype must have been Gg

15. Dihybrids More than 2 traits are crossed at a time.

16. T = tall t = short G = green g = yellow What is the genotype for a heterozygous tall and green pea plant? TtGg What gametes can it produce?

17. TtGg First Outer Inner Last TG TgtGtg

18. TGTgtGtg TG Tg tG tg Dihybrid Cross