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Question???. Be ready to quiz!. Genetics: Episode I A Monk, His Peas, and Genes. Ag Biology Sutherlin AST. Genetics. What is genetics? Branch of biology studying heredity What is heredity? Passing of traits from parent to offspring What are traits? Physical characteristics. Genetics.

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  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

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

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

  11. 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

  12. 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

  13. 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?

  14. 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?

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

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

  17. Mendel’s 7 Traits of Pea Plants

  18. 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

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

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

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

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

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

  24. 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!)

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

  26. Genetics • Monohybrid Punnett Square

  27. Genetics • Dihybrid Punnett Square

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