Genetics Problems 3

GENETICS PRACTICE 3: PROBABILITY PRACTICE 1. In humans, curly hair is dominant over straight hair. A woman heterozygous for hair curl marries a man with straight hair and they have children. a. What is the genotype of the mother? ________________________________________ b. What gametes can she produce? ___________________________________________ c. What is the genotype of the father? _________________________________________ d. What gametes can he produce? ____________________________________________ e. What is the probability that the 1st child will have curly hair? ______________________ f. What is the probability that the 2nd child will have curly hair? ______________________ 2. List all the gametes that are possible with each of the following genotypes. a. Aabb ___________________________ d. AABb ____________________________ b. AaBB ___________________________ e. AAbb ____________________________ c. AaBb ___________________________ f. aabb ____________________________ 3. What is the probability of getting the gamete (ab) from each of the following parents? a. Aabb ________________________________________________________________ b. aaBb ________________________________________________________________ c. AaBb ________________________________________________________________ d. AABb ________________________________________________________________ e. AAbb ________________________________________________________________ 4. In a certain strain of mice, black coat (B) is dominant over white coat (b). Describe what you would do to determine the genotype of a male with a black coat and how this would enable you to choose between the genotypes BB or Bb. _________________________________________________________________________ _________________________________________________________________________ _________________________________________________________________________ 5. What is the probability of each of the following sets of parents producing the given genotypes in their offspring? Parents Genotype Offspring Genotype Aa x Aa Aa Aa x aa Aa AaBb x AaBB AABB AaBb x AABb aabb AaBb x AaBb AaBb Probability 6. If an offspring has the genotype Aa, what possible combinations of parental genotypes could have produced this offspring? _________________________________________________________________________ 7. In corn, the trait for tall plants (T) is dominant to the trait for dwarf plants (t) and the trait for colored kernels (C) is dominant to the trait for white kernels (c). In a particular cross of corn plants, the probability of an offspring being tall is 1/2 and the probability of a kernel being colored is 3/4. Which of the following most probably represents the parental genotype? Include your work to show how you derived your solution. a. TtCc x ttCc b. TtCc x TtCc c. TtCc x ttcc d. TTCc x ttCc e. TTCc x TtCC 8. In humans, the allele for albinism (lack of pigment) is recessive to the allele for normal skin pigmentation. a. If two heterozygous parents have children what is the chance that a child will be albino? _______________________ b. If the child is normal, what is the chance that it is a carrier (heterozygous) for the albino allele? _______________________ c. If normal parents have an albino child, what is the probability that their next child will be normal for pigment? _______________________ EXTRA CREDIT In a cross between a female AaBbccDdee and a male AabbCcDdee, what proportion of the progeny will be the same phenotype as the female parent? (Assume independent assortment of all genes and complete dominance).