Genetics: Mendel & Punnett Squares

1. Genetics: Mendel & Punnett Squares Graded notes

2. Review Meiosis 2 mitosises, chromosomes replicated in interphase 1, homologous pairs, crossing over, 4 haploid daughter cells

3. Review Meiosis Pair of homologous chromosomes vs. homologous chromosomes….s phase…..

4. Genetics: Mendel Gregor Mendel: Austrian Monk who studied pea plants

5. Genetics: Mendel • Pea plants • (1st Mendel did this: ) • True-breeding:if self-pollinate, produce offspring identical to themselves • Cross pollinate:male sex cells in pollen from one plant fertilize egg cells of flower in another plant • (Then he tested flowers together w/2 different characteristics; purple/white) • Traits:specific characteristics • (seed color, height, texture)

6. Monohybrid Cross Mono = one trait (flower color) Hybrid = Offspring of two different breeding varieties Mendel reasoned that F1 plants carried two factors for the flower color trait (Purple and White). “Factors” called genes

7. Mendel's Crosses Mendel’s crosses: P:Parental generation F1:Offspring or 1st generation Hybrids:Offspring of crosses between parents with different traits Testing of other traits…one trait disappears in F1, Reappears in F2

8. Mendel's Crosses Conclusions of Mendel’s crosses: Genes:Chemical factors that determine traits passes on from one generation to another Alleles:Different forms of genes for trait Ex. Plant height has two forms produces tall plants & short ones

9. Alleles on Homologous chromosomes

10. Genes: Overview

11. Genes: Overview

12. Mendel's Crosses Principle of Dominance:states that some alleles are dominant and other are recessive Dominant: Trait will always show up; Shown with capital letters Recessive: Trait does not show up; Shown with lower case letters

13. Mendel's Crosses Homozygous: (TT) organism has 2 identical alleles for particular trait Heterozygous: (Tt) organism has 2differentalleles for particular trait Phenotype: physical characteristics you see (yellow, round) Genotype: genetic makeup (Tt); what we write

14. Genetics: Review Don’t Copy What are alleles? Different forms of gene Where do alleles come from? One from each parent Since one allele is inherited from each parent, two letters are needed to represent the alleles of a gene GENOTYPE? -two letters that represent the alleles of a gene EX. RR, Rr, rr

15. Genetics Review Don’t copy Phenotype? the outward appearance of an organism (what it looks like) If a farmer has a red flower (RR)give genotype and phenotype - the genotype is RR - the phenotype is red

16. Genetics Review

17. Genetics Review 1. A brown dog (bb) the genotype ________ the phenotype _______ 2. A long haired cat (Hh) the genotype _______ the phenotype _______

18. Principle of Segregation (Review) Mendel learned that the alleles of each individual separate and end up in gametes because of MEIOSIS!! Replication of chromosomes

19. Principle of Segregation Ex. A female pure brown dog (bb) Dominant or Recessive? bb b b

20. Y y Principle of Segregation PRACTICE on paper A hybrid male yellow canary (Yy)  Dominant? Y y

21. r r Principle of Segregation Practice! A pure female white flower (rr) Dominant? Recessive? r r

22. Principle of Segregation If a male red flower (Rr) and a female pure white (rr) flower from above got their gametes together (fertilization) What kind of combinations could be formed? X Practice on own paper before showing next slide! Write out male=Rr, female=rr. Which is dominant, recessive? What are we crossing? (Write Genotypes)

23. Male red flower (Rr) Female white flower (rr) Principle of Segregation Rr rr r r R r Sperm 1 Sperm 2 Egg 1 Egg 2 Answers? Write out alleles for each gamete of cross.

24. Principle of Segregation Show possible offspring of crossing different alleles. Genotype Phenotype r R + = 1 1 R + r = 1 2 r + r = 2 1 r + r = 2 2

25. What is a Punnett Square A punnet square is a chart that helps us predict the probability that an offspring with a particular genotype and phenotype will be produced Punnett Squares show the chances that one male’s sperm & one female’s eggs can make certain offspring

26. Drawing a Punnett Square Create a punnett square using male red (Rr) and female white (rr) flowers. To Make a punnet square there are a few simple steps to follow: 1) Draw a box and divide it into four parts

27. R r Drawing a Punnett Square 2) Label the left hand side of the box with the genotype of male parent (R=Red, r=White)

28. r r R r Drawing a Punnett Square 3) Label the top of the box with the genotype of the female parent

29. r r R r Drawing a Punnett Square 4) In the middle boxes place 2 alleles. One letter comes from the left side and one from the top You have predicted what kind of offspring these 2 parents could have!!! Rr Rr r r r r R= Red r= White Red______% White______%

30. r r R r Interpreting a Punnett Square You now know the possible genotypes for the offspring of these two parents. • The genotypes of the offspring are: 2: Rr, 2: rr Red=50% White=50% Rr Rr • The phenotypes of the offspring are: r r r r 2: Red, 2: White

31. Practice Problems 1. A cross between a female with straight hair (SS) and a male with curly hair (ss). Draw out punnett square: genotypes_____________ phenotypes______________ Straight______% Curly_______%

32. Practice Problems 2. A cross between a black dog (Bb) and a brown dog (bb). Draw out Punnett Square. genotypes_____________ phenotypes_______________ Black_______% Brown________% Ratio_____:______

33. Practice Problems 3. A cross between a yellow corn (Yy) and another yellow corn (Yy) (y = white corn). Draw out Punnett Square. genotypes_________________ phenotypes_________________ Yellow corn_______% White corn________% Ratio_____:______