DIHYBRID CROSSES, Exercises of Genetics

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What is a dihybrid cross?

A dihybrid cross is a cross among two traits.

DI= TWO HYBRID= COMBINATION Remember, Punnett squares are prediction tools used to determine probability of offspring for traits. Problem : Show the possible genetic combinations among offspring of a man who is heterozygous for both dimples and freckles, and a woman who is recessive for dimples and freckles. ♂ Ff Dd x ♀ ff dd

Setting a dihybrid cross FfDd x ffdd FD Fd fD fd fd fd fd fd FfDd Ffdd ffDd ffdd FfDd FfDd FfDd Ffdd Ffdd^ Ffdd ffDd ffDd ffDd ffdd ffdd ffdd Which percentage of offspring can be predicted to have freckles (F) AND dimples (D)? 4 out of 16 or 25% Which percentage of offspring can be predicted to have freckles (F) but NO dimples (d)? 4 out of 16 or 25% Which percentage of offspring can be predicted to have dimples (D) but NO freckles (f)? 4 out of 16 or 25% Which percentage of offspring can be predicted to have no freckles (f) nor dimples (d)? 4 out of 16 or 25%

Try this… In guinea pigs, short hair (S) is dominant over long hair (s) and black fur (B) is dominant to white fur (b). Cross two heterozygous individuals.

1. Parent genotypes _____________ X ______________
2. Assort Alleles:
3. Set up and Do Punnett Square
4. What are the possible Phenotypes?