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Punnett Squares ~Using Punnett squares to predict genetic outcomes .

Punnett Squares ~Using Punnett squares to predict genetic outcomes. Monohybrid Cross Complete Dominance. Two plants are crossed for the trait of height. One is purebred tall the other purebred short. We want to determine which trait is dominant. Monohybrid Cross Complete Dominance. 1.

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Punnett Squares ~Using Punnett squares to predict genetic outcomes .

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  1. Punnett Squares ~Using Punnett squares to predict genetic outcomes.

  2. Monohybrid Cross Complete Dominance Two plants are crossed for the trait of height. One is purebred tall the other purebred short. We want to determine which trait is dominant.

  3. Monohybrid Cross Complete Dominance 1 2 3 4 T T P 1 t T = Tall t = short t

  4. Monohybrid Cross Complete Dominance 1 2 3 4 T T F 1 t Tt T = Tall t = short t

  5. Monohybrid Cross Complete Dominance 1 2 3 4 T T F 1 t Tt Tt T = Tall t = short t

  6. Monohybrid Cross Complete Dominance 1 2 3 4 T T F 1 t Tt Tt T = Tall t = short Tt t

  7. T T F Monohybrid Cross Complete Dominance 1 t Tt Tt T = Tall t = short 1 2 Tt Tt t 3 4

  8. T T F Monohybrid Cross Complete Dominance 1 t Tt Tt T = Tall t = short t Tt Tt

  9. T T Tt Tt Monohybrid Cross Complete Dominance t 1 2 Tt Tt t 3 4 TT Tt tt Genotype ratio - 0 : 4 : 0 Phenotype ratio - 4 : 0 This cross results in offspring who are all tall. Tall Short

  10. Monohybrid Cross Complete Dominance If two F1 offspring are crossed, what will be the ratio of tall plants to short plants in the F2 generation ?

  11. t T F Monohybrid Cross Complete Dominance 1 T 1 2 t 3 4 T = Tall t = short

  12. t T F Monohybrid Cross Complete Dominance 2 T 1 2 t 3 4 TT T = Tall t = short

  13. t T F Monohybrid Cross Complete Dominance 2 T 1 2 t 3 4 TT Tt T = Tall t = short

  14. t T F Monohybrid Cross Complete Dominance 2 T 1 2 t 3 4 TT Tt T = Tall t = short Tt

  15. t T F Monohybrid Cross Complete Dominance 2 T TT Tt 1 2 Tt tt t 3 4 T = Tall t = short

  16. t T F Monohybrid Cross Complete Dominance 2 T 1 2 t 3 4 TT Tt T = Tall t = short Tt tt

  17. t T TT Tt Monohybrid Cross Complete Dominance T 1 2 Tt tt t 3 4 TT Tt tt Genotype ratio - 1 : 2 : 1 Phenotype ratio - 3 : 1 This cross results in 75 % of the F2 offspring being tall & 25 % being short. Tall Short

  18. Monohybrid Cross Incomplete Dominance When incomplete dominance is the hereditary pattern there is not a dominant form of a trait. Each form is equally dominant. When two different forms of a trait are bred, blending occurs and a third form of the trait is created.

  19. Monohybrid Cross Incomplete Dominance One Red and one White flower are crossed. The hereditary pattern is incomplete dominance. What are the expected phenotpyes of the offspring ?

  20. Monohybrid Cross Incomplete Dominance Genotypes are written using only capital letters. A red plant would have an “RR” genotype whereas a white flower would have a “WW” genotype. A hybrid pink flower would have a “RW” genotype.

  21. P1 Monohybrid Cross Incomplete Dominance R R W W If a purebred red and a purebred white flower are crossed what are the expected phenotypes of their offspring ? R R - WW-

  22. F1 Monohybrid Cross Incomplete Dominance R R W W RW RW RW RW The offspring from this cross will each have an “RW” genotype and ...

  23. R R F1 W W Monohybrid Cross Incomplete Dominance RW RW RW RW ... have a pink phenotype.

  24. F2 Monohybrid Cross Incomplete Dominance R W R W RR RW When two hybrid F1 offspring are bred, the expected RW WW genotypes and phenotypes are shown in the Punnett square.

  25. Monohybrid Cross Codominance Codominance is a hereditary pattern in which there is no one form of a trait more dominant than another. If a hybrid organism is produced it exhibits both forms of the trait and no blending occurs. An example of this type of herditary pattern is shown in shorthorn cattle.

  26. Monohybrid Cross Codominance In shorthorn cattle an “R” represents a gene for red hair and a “W” represents a gene for white hair. A hybrid “RW” exhibits roan coat color. It has both red hairs and white hairs mixed throughout the coat.

  27. P1 Monohybrid Cross Codominance R R W W If a purebred red bull and a purebred white cow are crossed what are the expected phenotypes of their offspring ? R - Red Hair W- White Hair

  28. R R F1 W W Monohybrid Cross Codominance RW RW RW RW The offspring from this cross exhibit the roan coat color. This is not considered a third form of the trait because no new hair colors are produced.

  29. F2 Monohybrid Cross Codominance R W R W RR RW When two hybrid F1 offspring are bred, the expected RW WW genotypes and phenotypes are shown in the Punnett square.

  30. Dihybrid Cross When two different traits are inherited in an an organism we call this a dihybrid cross. We will use complete dominance as the hereditary pattern to demonstrate this cross. Let’s use two hybrid plants for the traits of height and flower color. They will have a genotype of TtRr. Remember that only half of this genetic information is passed down to the offspring.

  31. tR Tr Dihybrid Cross tr tr TR TR tR Tr There are four different ways that the genes can combine in each parent’s sex cells. It will require a much larger Punnett square to determine the expected genotypes of the offspring TtRr x TtRr

  32. Dihybrid Cross TR Tr tR tr TTRR TR This is how a Punnett Square is set up to determine expected genotypes of offspring. Tr tR tr

  33. TR Tr tR tr TTRR TTRr TtRR TtRr TR Dihybrid Cross TTRr TTrr TtRr Ttrr Tr tR TtRR TtRr ttRR ttRr tr Ttrr ttRr ttrr TtRr TtRr x TtRr There are 16 possible combinations of sex cells.

  34. Dihybrid Cross TR Tr tR tr TtRr x TtRr TR Tr tR tr TTRR TTRr TtRR TtRr There are four different phenotypes possible. TTRr TTrr TtRr Ttrr TtRR TtRr ttRR ttRr TtRr Ttrr ttRr ttrr

  35. Genetics and Heredity Review Traits are passed from parents to their offspring during reproduction. There are three hereditary patterns: Complete Dominance Incomplete Dominance Codominance Monohybrid crosses involve the inheritance of only one trait.

  36. Genetics and Heredity Review Dihybrid crosses involve the inheritance of two or more traits. A Punnett square determines the expected Genotypes of the offspring. Genotype refers to the genetic makeup of an individual. Phenotype refers to the physical appearance of the individual.

  37. Genetics and Heredity Review Heterozygous, or hybrid, refers to an individual with one dominant gene and one recessive gene for a trait (Tt). Homozygous, or purebred, refers to an individual with two dominant (TT) or two recessive (tt) genes for a trait. T- Tall Gene (Dominant) t - Short Gene (Recessive)

  38. Genetics and Heredity Review P1 refers to the parental generation. The F1 refers to the first family; P1’s children. F2 are produced when two F1 mate.

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