28
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?
  1. 0.25
  2. 0.5
  3. 0.75
  4. 1
29
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 Brussel 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). What is the probability that their son likes Brussel sprouts (in other words, cannot taste PTC)?
  1. 0
  2. 0.25
  3. 0.5
  4. 1
30
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 issue must the couple confront?
  1. scientific
  2. financial
  3. ethical
  4. educational
31
A couple has three daughters. What is the probability that the next child they have will be a daughter?
  1. 0%
  2. 25%
  3. 50%
  4. 100%
32
What is the probability that a couple will have three daughters?
  1. 12
  2. 13
  3. 16
  4. 18
33
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?
  1. complete dominance
  2. codominance
  3. incomplete dominance
  4. sex-linked
34
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?
  1. 75% of the flowers are blue and 25% of the flowers are red.
  2. 50% of the flowers are blue and 50% of the flowers are red.
  3. 75% of the flowers are red and 25% are blue.
  4. 25% of the flowers are blue, 50% of the flowers are violet, and 25% of the flowers are red.
35
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?
  1. Gray body and cinnabar eyes are dominant.
  2. Eye color is sex-linked.
  3. Body color is sex-linked.
  4. Gray body and red eyes are dominant.
36

This table shows the predicted number of body and eye color for fruit flies. It predicts that there will be 244 gray body and red eye individuals. It predicts that there will be 244 black body and cinnabar eye individuals. It predicts that there will be 244 gray body and cinnabar eye individuals. It predicts that there will be 244 black body and red eye individuals.

Female flies from the F1 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?

  1. The traits assort independently.
  2. The traits are located on the X chromosome.
  3. The traits are on the same chromosome.
  4. The female flies were homozygous for wild type alleles.
37

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
  1. 2
  2. 3
  3. 2,4
  4. 3,4
38
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. What are the phenotypes of the offspring and in what proportions?
  1. All the cats are yellow.
  2. All the cats are black.
  3. All the cats are calico.
  4. There is not enough information to answer the question.