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Dihybrid Crosses – Practice Name: __________________________________________ Period: _____ In rabbits, grey hair is dominant to white hair, and black eyes are dominant to red eyes. Write the phenotype for each genotype below. GG = BB = Gg = Bb = gg = bb = 1. What are the phenotypes of rabbits that have the following genotypes: Ggbb ____________________ ggBB ________________________ ggbb ____________________ GgBb _________________________ 2. A male rabbit homozygous dominant for hair and homozygous recessive for eyes is crossed with a female rabbit heterozygous for both traits. Determine the phenotypes and proportions in the offspring. How many out of 16 are: Grey, red eyed ____ Grey, black eyed ____ White, red eyed ____ White, black eyed ____ 3. A male rabbit has the genotype GgBb. Determine the gametes produced by this rabbit (the sperm would have these combinations of alleles) and describe how these sperm cells demonstrate the laws of segregation and independent assortment. 4. A female rabbit has the genotype ggBb. Determine the gametes (eggs) produced by this rabbit. 5. Use the gametes from #3 and #4 to set up a Punnett square. Put the male's gametes on the top and the female's gametes down the side. Then fill out the square and determine what kind of offspring would be produced from this cross and in what proportion. Dihybrid Crosses – Practice Name: __________________________________________ Period: _____ 6. An aquatic arthropod called Cyclops has antennae that are either smooth or barbed. The allele for barbs is dominant. In the same organism, long tails are dominant to short tails. Show all the possible genotypes (and phenotypes) of this organism. Use the rabbit key to help you if you’re lost. 7. A Cyclops that has a short tail and smooth antennae is crossed with one that is heterozygous for both traits. Show the genotypes of the parents. ______________ x _______________ 8. Set up a Punnett square for the cross in #7. 9. A Cyclops that is true breeding for the barbed gene (BB) and long-tailed (TT) is crossed with one that is not barbed and long-tailed (Tt)? How many of the offspring will be barbed and long-tailed? Use a Punnett square to find the answer! ______________________________ 10. If two Cyclops that are heterozygous for both traits are crossed, what are the resulting phenotypes and in what proportion?
