mendlenotes.notebook
December 10, 2015
Mendel’s Dihybrid Crosses
• He used Peas that differed from each other by 2 traits instead of just one.
• The question he was asking: Will the two traits stay together in the next generation or will they be inherited independently of each other?
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mendlenotes.notebook
December 10, 2015
Dihybrid Cross Experiment
• Characteristics: True­bred round, yellow seeds and a true­
bred wrinkled, green seeds
• He already knew: Round and Yellow were dominant from his monohybrid crosses.
• Results: All Seeds were round and yellow.
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mendlenotes.notebook
December 10, 2015
Dihybrid Cross Experiment #2
• Allow the F1 generation to self pollinate.
• Results were that F2 varied greatly: round/yellow seeds, wrinkled/green seeds, round/green seeds, and wrinkled/
yellow seeds.
• In the F2 generation he again counted a definite ratio of physical characteristics: 9 round/yellow, 3 round/green, 3 wrinkled/yellow, and 1 wrinkled/green (9:3:3:1)
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mendlenotes.notebook
December 10, 2015
Conclusions to Dihybrid
Cross Experiments
• Mendel was able to express his second Law from the results and he called it: The Law of Independent Assortment
• Genes of different traits are inherited independently
• Why was he able to make this conclusion? Because if the alleles for seed shape and color were inherited together only 2 kinds of pea seeds would have been produced instead of variations of all combinations.
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mendlenotes.notebook
December 10, 2015
Dihybrid Cross Punnet Square
Example: What happens if a man who is heterozygous brown eyes AND heterozygous tongue roller has children with a woman who is homozygous blue eyes AND heterozygous tongue roller?? What is the chance that their child will be a blue eyed non­tongue roller?
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mendlenotes.notebook
December 10, 2015
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