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 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.

3. End Show 11-2 Probability and Punnett Squares Slide 3 of 21 Copyright Pearson Prentice Hall Punnett Squares Punnett squares can be used to predict and compare the genetic combinations that will result from a cross.

4. End Show 11-2 Probability and Punnett Squares Slide 4 of 21 Copyright Pearson Prentice Hall A capital letter represents the dominant allele for tall plant A lowercase letter represents the recessive allele for short plant In this example: T = tall t = short Punnett Squares

5. End Show 11-2 Probability and Punnett Squares Slide 5 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. Tt = parent 1 Punnett Squares Tt = parent 2

6. End Show 11-2 Probability and Punnett Squares Slide 6 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 Homozygous = true-breeding Heterozygous = hybrids

7. End Show 11-2 Probability and Punnett Squares Slide 7 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 (the genes) In Mendel’s plants there were 3 genotypes: TT, Tt, tt

8. End Show 11-2 Probability and Punnett Squares Slide 8 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

9. End Show 11-2 Probability and Punnett Squares Slide 9 of 21 Copyright Pearson Prentice Hall Time for a quiz!!!!!!!!!! 1. A piece of DNA that codes for a trait is called a _______________.

10. End Show 11-2 Probability and Punnett Squares Slide 10 of 21 Copyright Pearson Prentice Hall Time for a quiz!!!!!!!!!! 1. A piece of DNA that codes for a trait is called a gene.

11. End Show 11-2 Probability and Punnett Squares Slide 11 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_____

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 gene 2. The different forms of genes are called alleles

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 2. The different forms of genes are called alleles 3. The 2 alleles an organisms has for a trait _________________

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 alleles 3. The 2 alleles an organisms has for a trait genotype

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 3. The 2 alleles an organisms has for a trait genotype 4. The physical appearance of a trait________

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 genotype 4. The physical appearance of a trait phenotype

17. End Show 11-2 Probability and Punnett Squares Slide 17 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_______

18. End Show 11-2 Probability and Punnett Squares Slide 18 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

19. End Show 11-2 Probability and Punnett Squares Slide 19 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________

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 F 5. Recessive allele f

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 5. Recessive allele f 6. Homozygous flat nose genotype________

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 f 6. Homozygous flat nose genotype FF

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 6. Homozygous flat nose genotype FF 7. Heterozygous flat nose genotype________

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 FF 7. Heterozygous flat nose genotype Ft

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 7. Heterozygous flat nose genotype Ft 8. Pointy nose genotype_______________

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 Ff 8. Pointy nose genotype ff

27. End Show 11-2 Probability and Punnett Squares Slide 27 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________

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_______ 5. Recessive allele________ 6. Homozygous flat nose genotype________ 7. Heterozygous flat nose genotype________ 8. Pointy nose genotype_______________

29. End Show 11-2 Probability and Punnett Squares Slide 29 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). F2

30. End Show 11-2 Probability and Punnett Squares Slide 30 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. The T and t alleles for each parent (Tt) separated and each could give a T or t, creating the three possibilities – TT, Tt, & tt

31. End Show 11-2 Probability and Punnett Squares Slide 31 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.