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Punnett Squares

Punnett Squares. Gene vs. Allele. Alleles (variations of trait) -Purple, blue, white -curly, straight, wavy -Short, tall. Gene (trait) -Flower Color -Hair type -Plant Height. Create a gene and a corresponding allele on your whiteboard Gene: _____________ Allele: ________, _________.

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Punnett Squares

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  1. Punnett Squares

  2. Gene vs. Allele Alleles (variations of trait) -Purple, blue, white -curly, straight, wavy -Short, tall Gene (trait) -Flower Color -Hair type -Plant Height Create a gene and a corresponding allele on your whiteboard Gene: _____________ Allele: ________, _________

  3. Phenotype vs. Genotype • Phenotype • Physical appearance terms • ex. Tall, short, brown hair etc. • Genotype • Genes in cell, written with letters that represent the genes (ex: “T” for tall, or “t” for short)

  4. Predicting Inheritance • Punnett Squares: diagram that determines the probable distribution of inherited traits in the offspring. • UPPERCASE letters are used to represent dominant genes (traits). • lowercase letters are used to represent recessive genes (traits).

  5. Homozygous vs. Heterozygous • Homozygous: Both alleles are the same. Either both capitols (dominant) or both lower-cased (recessive) • Example: • BB (homozygous dominant) • bb (homozygous recessive) • Heterozygous: Both alleles are different. One capital letter and one lower-cased letter. • Example:Bb

  6. White board practice

  7. Write Het or Hom for the following genotypes • RR= • Ll= • Yy • Ee

  8. Write the genotypes for the following organisms. USE the letter R • A fish is homozygous recessive for fin color • A cat is heterozygous for tail length. • A turtle is homozygous dominant for shell color. • A polar bear is homozygous recessive for claw length.

  9. Predicting Inheritance • Sample Problem • T represents the gene for TALL in pea plants • t represents the gene for short in pea plants • So: • TT & Tt both result in a TALL plant, because T is dominant over t. • t is recessive. • What will tt result in? • Remember there are two genes for every trait!

  10. White board practice

  11. Sample Problems • Write the 3 possible genotypes and phenotypes for the following: • Green eyes are dominant to blue eyes • (use the first letter of the dominant trait) • GG= • Gg= • gg=

  12. Sample Problems • Write the 3 possible genotypes and phenotypes for the following: • Curled toes are dominant to straight toes • (use the first letter of the dominant trait) • CC= • Cc= • Cc=

  13. Predicting Inheritance Let’s cross a homozygous tall plant (TT) with a short plant (tt). Each plant will give only one of its’ two genes to the offspring. TT x tt T T t t

  14. Mendels’ “Law” of Segregation Each gene (allele) separates from the other so that the offspring get only one gene from each parent for a given trait. TT x t t T T t t T T t t

  15. PunnetSqaures • Predict the offspring if a tall plant (TT) is crossed (mates) with a short plant (tt) TT x tt

  16. Cross TT xtt by using a Punnett Square The genes from one parent go here. The genes from the other parent go here.

  17. Cross TT xtt by using a Punnett Square

  18. Punnett Squares If a box receives a capital letter and a lower-cased letter we write the capitol letter first

  19. Interpreting the Results Possible offspring Genotype =

  20. Interpreting the Results Possible offspring Genotype = Tt.

  21. Interpreting the Results Possible offspring Genotype = Tt. What percent of offspring will have the following genotypes: TT= Tt= tt=

  22. Interpreting the Results Possible offspring Genotype = Tt. What percent of offspring will have the following genotypes: TT= 0% Tt= 100% tt= 0%

  23. Interpreting the Results Possible offspring Genotype = Tt. What percent of offspring will have the following genotypes: TT= 0% Tt= 100% tt= 0% Possible offspring phenotype =

  24. Interpreting the Results Possible offspring Genotype = Tt. What percent of offspring will have the following genotypes: TT= 0% Tt= 100% tt= 0% Possible offspring phenotype = tall.

  25. Interpreting the Results Possible offspring Genotype = Tt. What percent of offspring will have the following genotypes: TT= 0% Tt= 100% tt= 0% Possible offspring phenotype = tall. What percent of offspring will have the following phenotypes: Tall= Short=

  26. Interpreting the Results Possible offspring Genotype = Tt. What percent of offspring will have the following genotypes: TT= 0% Tt= 100% tt= 0% Possible offspring phenotype = tall. What percent of offspring will have the following phenotypes: Tall= 100% Short= 0%

  27. Practice Problem Black rabbits are dominant to brown. Two heterozygous rabbits have offspring. Predict what percentage of their offspring will be brown.

  28. Practice Problem Black rabbits are dominant to brown. Two heterozygous rabbits have offspring. Predict what percentage of their offspring will be brown. Step 1: Determine the genotype of parents. Always use the first letter of the dominant trait. ____________x _____________

  29. Practice Problem Black rabbits are dominant to brown. Two heterozygous rabbits have offspring. Predict what percentage of their offspring will be brown. Step 1: Determine the genotype of parents. Always use the first letter of the dominant trait. ____________x _____________

  30. Step 2: Set up a Punnett Square

  31. Step 2: Set up a Punnett Square Step 3: Complete Punnett Square

  32. Step 4: Predict offspring phenotype.

  33. Practice Problem Black rabbits are dominant to brown. Two heterozygous rabbits have offspring. Predict what percentage of their offspring will be brown?

  34. White board practice

  35. Your Turn!! • Tall plants are dominant to short. Cross two heterozygous pea plants. 1. Determine parent’s genotype and write on whiteboard

  36. Set up a punnett square and fill it in. • Hold up whiteboard

  37. Punnett Squares

  38. Determine the genotype percentages and write on whiteboard • TT= • Tt= • Tt=

  39. Punnett Squares Genotype percentage : TT – 25%

  40. Punnett Squares Genotype percentage: TT – 25%, Tt – 50%

  41. Punnett Squares Genotype percentage: TT – 25%, Tt – 50%, tt – 25%

  42. Determine the Phenotype percentages and write on whiteboard • Tall= • Short=

  43. Punnett Squares Genotype percentage: TT – 25%, Tt – 50%, tt – 25% Phenotype percentage: Tall – 75%

  44. Punnett Squares Genotype percentage: TT – 25%, Tt – 50%, tt – 25% Phenotype percentage: Tall – 75%, short – 25%

  45. One More Whiteboard Practice Round seeds are dominant to wrinkled seeds. • Rr x rr    What percentage of the offspring will be round? _______________

  46. Assignments • Classwork: Punnett Packet Pages 1-? • Homework: Punnett Packet Pages ?-? (due tomorrow)

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