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Mendelian Genetics

Mendelian Genetics. The principles of probability can be used to predict the outcome of genetic crosses Probability - The likelihood that a particular event will occur is called probability. When a baby is born, the probability that it is a girl is 1:2 or 50%. Probability and Genetics.

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Mendelian Genetics

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  1. Mendelian Genetics The principles of probability can be used to predict the outcome of genetic crosses Probability - The likelihood that a particular event will occur is called probability. When a baby is born, the probability that it is a girl is 1:2 or 50%.

  2. Probability and Genetics Probability and Product Rule: How do you calculate the probability of more than one event occurring? Product Rule = Multiply the probability of each independent event together

  3. Probability and Genetics • Example: What is the chance that a couple (both heterozygous for tongue rolling) will produce a baby girl who can roll her tongue?

  4. Probability and Genetics 50% or 1/2 Begin by determining the probability of each event happening independently: What is the probability of producing a baby girl? ____________

  5. Probability and Genetics R r 75% or 3/4 R r RR Rr Rr rr What is the chance that a couple (both heterozygous for tongue rolling) will produce a child who can roll its tongue? Set up a Punnett Square! ________________

  6. Probability and Genetics ½ x ¾ = 3/8 ½ x ¼ = 1/8 The original question: What is the chance that a couple (both heterozygous for tongue rolling) will produce a baby girl who can roll her tongue? ________________ What is the chance that this couple will produce a baby girl who cannot roll her tongue? ________________

  7. Gregor Mendel • Mendel began his genetic research by crossing true-breeding pea plants, the P(arent) generation. • The result of this cross is the F1 generation, which are hybrids. • He next crossed the F1 generation to produce the F2 generation.

  8. Mendel’s Genetic Crosses P generation F1 generation F2 generation

  9. Mendel’s Research on 1 Trait • What is the phenotype ratio of F2 generation? • What is the genotype ratio of F2 generation? 3 violet flowers:1 white flower 1 BB: 2Bb: 1bb

  10. Mendel’s Law of Segregation • Mendel recognized that each pea plant had two alleles for a trait. • He hypothesized that one allele came from each of the two parent plants. • Mendel’s law of segregation states: Allele pairs separate during gamete (sex cell) formation, and randomly unite at fertilization.

  11. Production of Gametes Half the number of chromosomes as the parent cell

  12. The Two-Factor Cross • Mendel next tested whether the segregation of alleles for one trait (example seed shape: round or wrinkled) affects the segregation of a second trait (example seed color: yellow or green)

  13. The Two-Factor Cross • One plant was true breeding for both yellow AND round seeds = P generation • This plant’s genotype was YYRR • The only alleles that could be produced by this plant were… • YR

  14. The Two-Factor Cross • The second plant was true breeding for both wrinkled AND green seeds = P generation • This plant’s genotype was yyrr • The only alleles that could be produced by this plant were… • yr

  15. The Two Factor CrossThe only possible result of this cross is … • RrYy = F1 generation • What is the phenotype of the offspring? • Round and yellow seeds. RY RY RrYy RrYy ry ry RrYy RrYy

  16. The Two-Factor Cross • Mendel next crossed the offspring of the F1 generation. He crossed YyRr with YyRr. Each plant is called a dihybrid. • Which alleles are created from YyRr? • Work this out on your whiteboard! • YR • yR • yR • yr

  17. The Two Factor Cross YR yR Yr yr • Draw a 16 box Punnett Square to show the cross between YyRr and YyRr • Begin by showing the possible alleles. • Then fill in the boxes! YR yR Yr yr r yr

  18. Two Factor Cross Results

  19. The Two Factor Cross • What is the phenotype ratio for a two factor cross between dihybrids? Write on whiteboard! • ___________dominant for both traits – yellow and round seeds • ___________dominant for one trait and recessive for the second – yellow and wrinkled seeds 9 3

  20. The Two Factor Cross 3 • ___________recessive for one trait and dominant for the second – green and round • ___________recessive for both traits – green and wrinkled 1 • Phenotype ratio – 9:3:3:1

  21. Mendel’s Actual Results

  22. Mendel’s 4th Conclusion Principle of Independent Assortment - genes for different traits can segregate INDEPENDENTLY during the formation of gametes. For example: A person can have blonde hair and blue eyes or brown hair and blue eyes. Hair color and eye color are inherited independently of each other.

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