1. End Show Slide 1 of 21 Copyright Pearson Prentice Hall 11-2 Probability and Punnett Squares

2. End Show 11-2 Probability and Punnett Squares Slide 2 of 21 Copyright Pearson Prentice Hall How do geneticists use the principles of probability? Genetics and Probability

3. End Show 11-2 Probability and Punnett Squares Slide 3 of 21 Copyright Pearson Prentice Hall Genetics and Probability The likelihood that a particular event will occur is called probability. The principles of probability can be used to predict the outcomes of genetic crosses.

4. End Show 11-2 Probability and Punnett Squares Slide 4 of 21 Copyright Pearson Prentice Hall Punnett Squares How do geneticists use Punnett squares?

5. End Show 11-2 Probability and Punnett Squares Slide 5 of 21 Copyright Pearson Prentice Hall Punnett Squares The gene combinations that might result from a genetic cross can be determined by drawing a diagram known as a Punnett square. Punnett squares can be used to predict and compare the genetic variations that will result from a cross.

6. End Show 11-2 Probability and Punnett Squares Slide 6 of 21 Copyright Pearson Prentice Hall A capital letter represents the dominant allele for tall. A lowercase letter represents the recessive allele for short. In this example, T = tall t = short Punnett Squares

7. End Show 11-2 Probability and Punnett Squares Slide 7 of 21 Copyright Pearson Prentice Hall Gametes produced by each parent are shown along the top and left side. Each parent plant has a T and t allele to give to the F1 offspring. Punnett Squares

8. End Show 11-2 Probability and Punnett Squares Slide 8 of 21 Copyright Pearson Prentice Hall Punnett Squares Possible gene combinations for their offspring appear in the four boxes. Organisms that have two identical alleles for a particular trait are said to be homozygous. TT or tt Organisms that have two different alleles for the same trait are heterozygous. Tt

9. End Show 11-2 Probability and Punnett Squares Slide 9 of 21 Homozygous organisms are true – breeding for a particular trait. Heterozygous organisms are a hybrid for a particular trait. Copyright Pearson Prentice Hall

10. End Show 11-2 Probability and Punnett Squares Slide 10 of 21 Copyright Pearson Prentice Hall Punnett Squares Phenotype: the physical characteristic (trait) of an organism. In Mendel’s plants there are 2 phenotypes: tall and short. Genotype: the genetic make-up of the organism In Mendel’s plants there were 3 genotypes: TT, Tt, tt

11. End Show 11-2 Probability and Punnett Squares Slide 11 of 21 Copyright Pearson Prentice Hall Punnett Squares The tall plants have different genotypes (TT and Tt), but they have the same phenotype (tall). TT Homozygous Tt Heterozygous

12. End Show 11-2 Probability and Punnett Squares Slide 12 of 21 Copyright Pearson Prentice Hall Time for a quiz!!!!!!!!!! 1. A piece of DNA that codes for a trait is called a _______________.

13. End Show 11-2 Probability and Punnett Squares Slide 13 of 21 Copyright Pearson Prentice Hall Time for a quiz!!!!!!!!!! 1. A piece of DNA that codes for a trait is called a gene.

14. End Show 11-2 Probability and Punnett Squares Slide 14 of 21 Copyright Pearson Prentice Hall Time for a quiz!!!!!!!!!! 1. A piece of DNA that codes for a trait is called a gene. 2. The different forms of genes are called_____

15. End Show 11-2 Probability and Punnett Squares Slide 15 of 21 Copyright Pearson Prentice Hall Time for a quiz!!!!!!!!!! 1. A piece of DNA that codes for a trait is called a gene 2. The different forms of genes are called alleles

16. End Show 11-2 Probability and Punnett Squares Slide 16 of 21 Copyright Pearson Prentice Hall Time for a quiz!!!!!!!!!! 1. A piece of DNA that codes for a trait is called a gene 2. The different forms of genes are called alleles 3. The 2 alleles an organisms has for a trait _________________

17. End Show 11-2 Probability and Punnett Squares Slide 17 of 21 Copyright Pearson Prentice Hall Time for a quiz!!!!!!!!!! 1. A piece of DNA that codes for a trait is called a gene 2. The different forms of genes are called alleles 3. The 2 alleles an organisms has for a trait genotype

18. End Show 11-2 Probability and Punnett Squares Slide 18 of 21 Copyright Pearson Prentice Hall Time for a quiz!!!!!!!!!! 1. A piece of DNA that codes for a trait is called a gene 2. The different forms of genes are called alleles 3. The 2 alleles an organisms has for a trait genotype 4. The physical appearance of a trait________

19. End Show 11-2 Probability and Punnett Squares Slide 19 of 21 Copyright Pearson Prentice Hall Time for a quiz!!!!!!!!!! 1. A piece of DNA that codes for a trait is called a gene 2. The different forms of genes are called alleles 3. The 2 alleles an organisms has for a trait genotype 4. The physical appearance of a trait phenotype

20. End Show 11-2 Probability and Punnett Squares Slide 20 of 21 Copyright Pearson Prentice Hall The trait is nose shape. Flat nose is dominant over pointy nose. Use letters F, f to show: 4. Dominant allele_______

21. End Show 11-2 Probability and Punnett Squares Slide 21 of 21 Copyright Pearson Prentice Hall The trait is nose shape. Flat nose is dominant over pointy nose. Use letters F, f to show: 4. Dominant allele F

22. End Show 11-2 Probability and Punnett Squares Slide 22 of 21 Copyright Pearson Prentice Hall The trait is nose shape. Flat nose is dominant over pointy nose. Use letters F, f to show: 4. Dominant allele F 5. Recessive allele________

23. End Show 11-2 Probability and Punnett Squares Slide 23 of 21 Copyright Pearson Prentice Hall The trait is nose shape. Flat nose is dominant over pointy nose. Use letters F, f to show: 4. Dominant allele F 5. Recessive allele f

24. End Show 11-2 Probability and Punnett Squares Slide 24 of 21 Copyright Pearson Prentice Hall The trait is nose shape. Flat nose is dominant over pointy nose. Use letters F, f to show: 4. Dominant allele F 5. Recessive allele f 6. Homozygous flat nose genotype________

25. End Show 11-2 Probability and Punnett Squares Slide 25 of 21 Copyright Pearson Prentice Hall The trait is nose shape. Flat nose is dominant over pointy nose. Use letters F, f to show: 4. Dominant allele F 5. Recessive allele f 6. Homozygous flat nose genotype FF

26. End Show 11-2 Probability and Punnett Squares Slide 26 of 21 Copyright Pearson Prentice Hall The trait is nose shape. Flat nose is dominant over pointy nose. Use letters F, f to show: 4. Dominant allele F 5. Recessive allele f 6. Homozygous flat nose genotype FF 7. Heterozygous flat nose genotype________

27. End Show 11-2 Probability and Punnett Squares Slide 27 of 21 Copyright Pearson Prentice Hall The trait is nose shape. Flat nose is dominant over pointy nose. Use letters F, f to show: 4. Dominant allele F 5. Recessive allele f 6. Homozygous flat nose genotype FF 7. Heterozygous flat nose genotype Ft

28. End Show 11-2 Probability and Punnett Squares Slide 28 of 21 Copyright Pearson Prentice Hall The trait is nose shape. Flat nose is dominant over pointy nose. Use letters F, f to show: 4. Dominant allele F 5. Recessive allele f 6. Homozygous flat nose genotype FF 7. Heterozygous flat nose genotype Ft 8. Pointy nose genotype_______________

29. End Show 11-2 Probability and Punnett Squares Slide 29 of 21 Copyright Pearson Prentice Hall The trait is nose shape. Flat nose is dominant over pointy nose. Use letters F, f to show: 4. Dominant allele F 5. Recessive allele f 6. Homozygous flat nose genotype FF 7. Heterozygous flat nose genotype Ff 8. Pointy nose genotype ff

30. End Show 11-2 Probability and Punnett Squares Slide 30 of 21 Copyright Pearson Prentice Hall Time for a quiz!!!!!!!!!! 1. A piece of DNA that codes for a trait is called a _______________. 2. The different forms of genes are called_____ 3. The 2 alleles an organisms has for a trait _________________ 4. The physical appearance of trait________

31. End Show 11-2 Probability and Punnett Squares Slide 31 of 21 Copyright Pearson Prentice Hall The trait is nose shape. Flat nose is dominant over pointy nose. Use letters F, f to show: 4. Dominant allele_______ 5. Recessive allele________ 6. Homozygous flat nose genotype________ 7. Heterozygous flat nose genotype________ 8. Pointy nose genotype_______________

32. End Show 11-2 Probability and Punnett Squares Slide 32 of 21 Copyright Pearson Prentice Hall Probability and Segregation One fourth (1/4) of the F 2 plants have two alleles for tallness (TT). 2/4 or 1/2 have one allele for tall (T), and one for short (t). One fourth (1/4) of the F 2 have two alleles for short (tt).

33. End Show 11-2 Probability and Punnett Squares Slide 33 of 21 Copyright Pearson Prentice Hall Probability and Segregation Because the allele for tallness (T) is dominant over the allele for shortness (t), 3/4 of the F 2 plants should be tall. The ratio of tall plants (TT or Tt) to short (tt) plants is 3:1. The predicted ratio showed up in Mendel’s experiments indicating that segregation did occur.

34. End Show 11-2 Probability and Punnett Squares Slide 34 of 21 Copyright Pearson Prentice Hall Probabilities Predict Averages Probabilities predict the average outcome of a large number of events. Probability cannot predict the precise outcome of an individual event. In genetics, the larger the number of offspring, the closer the resulting numbers will get to expected values.

35. End Show Slide 35 of 21 Copyright Pearson Prentice Hall 11-2 Probability can be used to predict a.average outcome of many events. b.precise outcome of any event. c.how many offspring a cross will produce. d.which organisms will mate with each other.

36. End Show Slide 36 of 21 Copyright Pearson Prentice Hall 11-2 Compared to 4 flips of a coin, 400 flips of the coin is a.more likely to produce about 50% heads and 50% tails. b.less likely to produce about 50% heads and 50% tails. c.guaranteed to produce exactly 50% heads and 50% tails. d.equally likely to produce about 50% heads and 50% tails.

37. End Show Slide 37 of 21 Copyright Pearson Prentice Hall 11-2 Organisms that have two different alleles for a particular trait are said to be a.hybrid. b.heterozygous. c.homozygous. d.recessive.

38. End Show Slide 38 of 21 Copyright Pearson Prentice Hall 11-2 Two F 1 plants that are homozygous for shortness are crossed. What percentage of the offspring will be tall? a.100% b.50% c.0% d.25%

39. End Show Slide 39 of 21 Copyright Pearson Prentice Hall 11-2 The Punnett square allows you to predict a.only the phenotypes of the offspring from a cross. b.only the genotypes of the offspring from a cross. c.both the genotypes and the phenotypes from a cross. d.neither the genotypes nor the phenotypes from a cross.