Question???

1. Question??? • Be ready to quiz!

2. Genetics: Episode IA Monk, His Peas, and Genes Ag Biology Sutherlin AST

3. Genetics • What is genetics? • Branch of biology studying heredity • What is heredity? • Passing of traits from parent to offspring • What are traits? • Physical characteristics

4. Genetics • Gregor Mendel • A monk, 1800’s Austria • First to study and determine factors of heredity • Used carefully controlled experiments: only changed one factor at a time

5. Genetics • Why peas? • Produce sexually • Male and female parts on same flower • Male parts are called? • Female parts are called?

6. Genetics • Pollination – male sex cells (pollen) lands on female parts (pistil) • Fertilization – DNA from pollen combines with DNA from ovum (egg) • Becomes seed

7. Genetics • Self-pollination: male and female sex cells come from same plant • Cross-pollination: sex cells come from two different plants • Create hybrid

8. Genetics • What did Mendel do? • Studied TALL traits and SHORT traits in plants (parents = P1) • Cross-pollinated these plants to get hybrids • ALL of the offspring (F1) were TALL

10. Genetics • What did Mendel do next? • Took the offspring (F1), then crossed them together • This time, not all offspring the same.

12. Genetics • What did Mendel do next? • ¾ of plants were tall • ¼ were short plants • This is called a 3:1 ratio

13. Genetics So what does this mean? • Unit Factors • Mendel concluded two factors control each trait • We know these are genes • One factor from the mother • One from the father

14. Genetics • Unit Factors • For each gene, there are alleles • Different forms of each gene • Example: there is a gene for height (T) It could be the Tall allele – T It could be the Short allele - t

15. Genetics • Unit Factors • Since we have two copies of each gene, three combinations • Two Tall (TT) alleles • Two Short (tt) alleles • One Tall allele and one short allele (Tt) But how is this possible?

16. Genetics What else does this mean? • Rule of Dominance • Only one allele is observable • Dominant alleles: observable trait • Recessive alleles: unobservable trait • So which is dominant for height in pea plants?

17. Genetics • So what does each look like? • TT: • tt: • Tt:

18. Genetics • What about cows? • If you cross purebred black angus cattle with red angus cattle, you get black cattle • What does this mean?

19. Mendel’s 7 Traits of Pea Plants

20. Genetics • Two organisms can look the same, but carrying different genes • Phenotype: how an organism looks (think physical) • Tall? Short? • Genotype: the genes an organism has • Tall: could be Tt • Tall: could be TT

21. Genetics • Homozygous – both alleles are the same • TT, tt • Heterozygous – alleles are different • Tt All of this, by a monk, in the 1800s!

22. Genetics • Dihybrid cross • Looking at just one trait (height) is monohybrid (one) • But what if we track more than one trait?

23. Genetics • Mendel’s Dihybrid Cross • Round peas (R=round, r=wrinkled) • Seed color (Y=yellow, y=green) Parents (P1) Round Yellow X Wrinkled Green

24. Genetics • Mendel’s Dihybrid Cross Parents (P1) Round Yellow X Wrinkled Green RRYY rryy Result? Offspring (F1) ALL Round Yellows RrYy

25. Genetics • Mendel’s Dihybrid Cross F1 Cross X So now what do you get?

27. Genetics • Mendel’s Dihybrid Cross • The point? • Law of Independent Assortment: genes for different traits are inherited independently of one another (green seeds do not have to be wrinkled!)

28. Genetics • Punnett Squares • Tool for projecting Phenotypes and Genotypes of offspring • Developed by Reginald Punnett (England)

29. Genetics • Monohybrid Punnett Square

30. Genetics • Dihybrid Punnett Square