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AP Biology Advanced Genetics Problems

1. If all of the offspring of a particular cross have the genotype Bb, what must the genotype of the parents be?

2. In purple people eaters, one-horn (H) is dominant and no horns (h) is recessive. If two heterozygotes mate, what will be the likely genotypic and phenotypic ratios of the offspring?

3. In certain cats, tail length is determined by a gene that demonstrates incomplete dominance. The allele that causes a long tail (T) is not completely dominant over the allele that causes no tail (t). If a cat is heterozygous for this trait, then the cat will have a short tail. What is the probability that the offspring will be manx cats (no tail) if a short-tailed cat is bred with a manx cat?

4. A woman has type A blood, and her husband has type B blood. Their child has type O blood. The husband claims the child can’t be his. Is he right?

5. Hemophilia is a disease caused by a gene found on the X chromosome. Therefore, it is referred to as a sex-linked disease. The recessive allele causes the disease. A normal man marries a woman that is heterozygous for the trait. Give the genotypes and phenotypes of all possible offspring.

6. Red-green color blindness is a sex-linked recessive trait. Suppose a man with the disease marries a woman who is a carrier for the disease. Will any of their children have the disease?

7. A certain breed of cow can be either red (R), white (W), or roan (incomplete dominance) and either have horns (H) or be hornless (h). The allele for horns dominates the allele for hornless. If a bull and cow are heterozygotes for both genes, what are the probabilities for each possible phenotype?

8. In humans, curly hair is dominant over straight hair. A woman heterozygous for hair curl marries a man with straight hair. Their first child has curly hair. What is the probability that the second child will have curly hair?

9. 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

10. 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 of BB or Bb.

11. Complete the following table to show the probability of each of the following sets of parents producing the given genotypes in their offspring:

|Parent’s Genotype |Offspring’s Genotype |Probability |

|AaBb x AaBB |AABB | |

|AaBb x AABb |aabb | |

|AaBb x AaBb |AaBb | |

12. In humans, the allele for abinism (lack of pigment) is recessive to the allele for normal skin pigmentation.

a. If two heterozygote 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 for the albino allele?

c. If normal parents have an albino child, what is the probability that their next child will be normal for pigmentation?

13. In a cross between a female AaBbccDdee and a male AabbCcDdee, what proportion of the offspring will be the same phenotype as the female parent? (Assume independent assortment of all genes and complete dominance).

14. Two blue Andalusian chickens are mated. Thirty-six eggs taken from the hen hatch into the following chicks: 10 white, 18 blue, and 8 black. Your hypothesis is that this is an example of incomplete dominance. Use chi-square to test you hypothesis. You must first determine the expected phenotype ratio of a cross involving incompletely dominant alleles.

BB = black; Bb = blue; bb = white

a. Write the null hypothesis.

b. Determine the degrees of freedom.

c. Report the calculated chi-square value.

d. Report the critical value. (Use probability = 0.05)

e. Write a conclusion based on the outcome of the chi-square analysis.

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