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Mendel’s Second Experiment

Mendel’s Second Experiment. Inheritance of Two Traits Dihybrid Cross. Monohybrid Review. How many traits were being looked at during the Mendel’s monohybrid cross? __________________________________ What was being crossed in Mendel’s monohybrid cross? _________________________________

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Mendel’s Second Experiment

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  1. Mendel’s Second Experiment Inheritance of Two Traits Dihybrid Cross

  2. Monohybrid Review • How many traits were being looked at during the Mendel’s monohybrid cross? • __________________________________ • What was being crossed in Mendel’s monohybrid cross? • _________________________________ • _________________________________

  3. Back Track for a Second • What exactly was a purebred species in terms of genotype? • It was a species that had the same alleles in its genetic makeup (either BB or bb) • What about a hybrid species in terms of genotype? • It was a species that had different alleles in its genetic makeup (like Bb)

  4. P X P • When the two parents were crossed, TT X tt, what resulted? • The Results were four heterozygous offspring. • These are the F1 generation

  5. F1 X F1 • When the two F1 generation were crossed, TT X tt, what resulted? • The Results were three dominant and one recessive in a 3:1 phenotypic ratio but in a 1:2:1 genotypic ratio • These are the F2 generation

  6. The Law of Segregation • What does the Law of Segregation state? • It states that inherited traits are determined by pairs of “factors” • These factors segregate (separate) in the gametes

  7. What happened next? • Mendel completed the monohybrid cross and started to ask and formulate new questions • What do you think he was thinking of next? • He wanted to know if the inheritance of one characteristic influenced the inheritance of a different characteristic

  8. What did he try next? • He started all over again • He produced purebred plants just like last time with the traits he wanted to examine • He bread pea plants that were round and yellow pure plants (dominant for both) and then he did the same for wrinkled and green (recessive for both)

  9. What did he try next? • He then crossed them again • The P X P ended up yielding what? • The F1 ended up being all yellow and all round, just like last time • There seems to be some similarity

  10. P X P Dihybrid Cross

  11. Then What? • Just like last time he crossed the two F1 Progeny • What do you think he got? • He got 9 Yellow and round • He got 3 Green and round • He got 3 Yellow and Wrinkled • He got 1 Green and Wrinkled

  12. What’s The Ratio? • The ratio that he got was? • 9:3:3:1

  13. How Many? • How many plants do you think that Mendel used for this experiment • 551 pea plants • And of that 551 this was the ratio that he got • 320 round and yellow • 104 round and green • 101 wrinkled and yellow • 26 wrinkled and green

  14. What did this tell him? • The ratio of 9:3:3:1 could be explained if the alleles from one trait were inherited independently of the alleles for another trait The Law of Independent Assortment

  15. The Law of Independent Assortment • The second law of inheritance states:_________________________________________________________________________________________________ • Different pairs of alleles are passed to the offspring independently of each other

  16. The Law of Independent Assortment • This means that offspring may have new combinations of alleles that are not present in either parent

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