Test Prep for AP® Courses

The trait for widow’s peak can be considered a monoallelic dominant trait in humans. If a man with a widow’s peak and a woman with a straight hairline have a child together, what is the probability that the child will inherit the widow’s peak if you know that the father’s mother had a straight hairline?

Don’t like Brussels sprouts? Blame your genes. The chemical PTC (phenylthiocarbamide), which is nearly identical to a compound found in the cabbage family, tastes very bitter for some people. Others cannot detect a taste. The ability to taste PTC is incompletely dominant and is controlled by a gene on chromosome 7.

A woman who finds Brussels sprouts mildly distasteful (in other words, who can taste PTC weakly) has a child with a man who hates Brussel sprouts (in other words, who can taste PTC strongly). Appy your understanding of patterns of incomplete dominance to predict the probability that their son likes Brussels sprouts (in other words, he cannot taste PTC).

Tay-Sachs disease is an autosomal recessive disorder that causes severe problems in neurons. Children who receive two copies of the gene rarely live beyond the age of five. There is no cure for the disease. During a genetic screening, a couple is told that both partners carry the recessive gene. What kind of benefit does this couple have by knowing this information?

A couple has three daughters. What is the probability that the next child they have will be a daughter?

A couple planning a family hopes to eventually have three children. What is the probability that the couple will have three daughters? Justify your claim with reasoning.

Petunias can be blue, red, or violet. When a blue flower is crossed with a red flower, all the resulting flowers are violet. When a violet flower is crossed with a red flower, about half of the flowers are violet and half are red. How do you characterize the color trait?

Petunias can be blue, red, or violet. When a blue flower is crossed with a red flower, all the resulting flowers are violet. Two violet petunias are crossed. Which is the most probable result of the cross?

Fruit flies (Drosophila melanogaster) with a wild-type phenotype have gray bodies and red eyes. Certain mutations can cause changes to these traits. Mutant flies may have a black body and/or cinnabar eyes. To study the genetics of these traits, a researcher crossed a true-breeding wild-typed male fly with a true-breeding female fly with a black body and cinnabar eyes. All of the F1 progeny displayed a wild type phenotype. Which of the following is correct about the traits observed?

Female flies from the $F_1$ generation were crossed with true-breeding male flies with black bodies and cinnabar eyes. The table represents the predicted outcome and the data obtained from the cross. What was the assumption that lead to the predicted numbers?

Cats can be black, yellow, or calico (black and yellow patches). Coat color is carried on the X chromosome. What type of inheritance is color coat in cats?

1. Complete dominance
2. Codominance
3. Incomplete dominance
4. Sex-linked

Cats can be black, yellow, or calico (black and yellow patches). Coat color is carried on the X chromosome. A yellow cat is crossed with a black cat. Assume that the offspring are both male and female. Identify the statement that best describes what you can predict for the phenotypes of the offspring, and the proportions of those phenotypes.