Biology: Life on Earth 7e
Student Self Test Questions and Answers
Chapter 12: Patterns of Inheritance
Self Test
1. Alleles are alternate forms of a gene. The alleles for the gene that determines blood type in humans are found at
__________.
a. different loci on homologous chromosomes
b. different loci on the same chromosome
c. the same locus on homologous chromosomes
2. Humans have about 35,000 genes. How many alleles of each of these genes are present in your muscle cells,
disregarding genes on the X and Y chromosomes?
a. 1
b. 2
c. 23
d. 46
3. If a plant is true-breeding for a flower color, it is __________ for the flower-color gene.
a. homozygous
b. heterozygous
c. dominant
4. A Punnett square is __________.
a. a method of crossing pea plants
b. a chart that can help you keep track of the alleles during genetic crosses
c. named after an Augustinian monk in Brno, Moravia (currently part of the Czech Republic)
5. If a gene has alleles that are incompletely dominant, an individual that is heterozygous at this locus will have
characteristics that are __________.
a. the same as organisms that are homozygous for the recessive allele
b. the same as organisms that are homozygous for the dominant allele
c. intermediate between organisms that are homozygous for the recessive allele and organisms
that are homozygous for the dominant allele
6. Which one of the following statements is true? (For extra practice, try to change the incorrect answers to make
them correct statements. Also, give an example for each of the correct statements.)
a. An allele is either dominant or recessive, not in between.
b. A particular gene can have only two alleles.
c. A single gene influences only a single trait.
d. A single trait can be affected by many different genes.
e. The environment is irrelevant to gene expression.
7. Cystic fibrosis is a recessive trait. Imagine that your friend Roger has cystic fibrosis but that his parents do not.
What do you know about Roger's alleles and those of his parents at the cystic fibrosis locus of their DNA?
a. This information is insufficient to allow me to conclude anything about the cystic fibrosis alleles in
the DNA of Roger's parents.
b. This information is insufficient to allow me to conclude anything about the cystic fibrosis alleles in
Roger’s DNA.
c. Roger is heterozygous and his parents are homozygous at the cystic fibrosis locus.
d. Roger is homozygous and his parents are heterozygous at the cystic fibrosis locus.
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
8. Anne Boleyn, King Henry VIII's second wife, was beheaded because she did not provide him with a son as an heir.
Explain why King Henry should have blamed himself and not his wife.
a. All of the sperm that males produce contain an X chromosome, so their genetic contribution to
the child determines its sex.
b. All of the eggs that females produce contain an X chromosome, so their genetic contribution to
the child does not determine its sex.
c. The eggs that females produce contain either an X or a Y chromosome, so their genetic
contribution to the child is unrelated to its sex.
9. In many cases, conditions that occur more frequently in males than in females are due to sex-linked inheritance.
Male pattern baldness is more common in males than in females, but that is not because of sex-linked inheritance.
Suggest a possible explanation.
a. An important gene for hair development must be on the X chromosome.
b. An important gene for hair development must be on the Y chromosome.
c. Male hormones affect expression of an important hair development gene.
10. Labrador retrievers may have yellow fur, chocolate brown fur, or black fur. Coat color is determined by two genes
that have two alleles each. One gene, called E, determines whether the dog’s fur is dark or light, with the dark allele
(E) dominant to the light allele (e). The other gene, called B, determines whether the dark fur will be black or
chocolate, with the black allele (B) dominant to the chocolate allele (b). If you mate two chocolate labs together, what
color puppies can they have?
a. Only chocolate puppies can be produced, because both parents must be EEbb.
b. Chocolate or yellow puppies can be produced, because the parents can be either Eebb or EEbb.
c. Chocolate, yellow, and black puppies will be produced, because both parents must be EeBb.
d. Chocolate and black puppies will be produced, because both parents must be EeBb.
11. A couple brings home their new, nonidentical twin daughters, Joan and Jill. After several months, the father
begins to suspect that there was a mix-up at the hospital, because Jill doesn’t look much like either parent or like her
sister. When the twins' blood tests come back, the father calls his lawyer to start a lawsuit against the hospital. The
mother, father, and Joan have type A blood, but Jill has type O blood. Does the father have a case? Explain your
answer. (The gene for blood type has three alleles: A, B, and O. The A and B alleles are codominant, and the O allele
is recessive.)
a. No, because parents with type A blood can have a child with type O blood.
b. No, because parents with any blood type (A, B, AB, or O) can produce children with type O
blood.
c. Yes, because all of this couple’s children will have type A blood.
d. Yes, because people with type A blood can pass on only A alleles to their children.
12. What are alleles?
a. specific physical locations of genes on a chromosome
b. variations of the same gene (i.e., similar nucleotide sequences on homologous chromosomes)
c. homozygotes
d. heterozygotes
13. Consider this hypothetical example: If you were to apply Mendel's reasoning to the past presidential election, and
hanging chads (C) were dominant to pregnant chads (c), which of the following genotypes would result in the
expression of the dominant phenotype from a cross of F 1 offspring that are Cc?
a. cc
b. CC
c. Cc
d. Both the first and third answers above are correct.
e. Both the second and third answers above are correct.
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
14. What does Mendel's law of independent assortment tell us about the behavior of genes during meiosis?
a. Alleles of a particular gene will be distributed to gametes randomly, independent of other genes
on different chromosomes.
b. Alleles on the same chromosome will be distributed to different gametes independently.
c. Independent assortment is synonymous with crossing over.
d. all of the above
15. If an organism has only three chromosomes, how many chromosomes are autosomes?
a. one
b. two
c. three
d. none
16. A single gene capable of influencing multiple phenotypes within a single organism is said to be __________.
a. codominant for that gene
b. incompletely dominant for that gene
c. polygenic for that gene
d. pleiotropic for that gene
17. What is the root cause of sickle-cell anemia?
a. mutations in the gene that directs the synthesis of the hemoglobin protein
b. an amino acid substitution in the hemoglobin protein
c. malaria
d. abnormally shaped red blood cells
18. If the pea plants I planted this year all have red flowers, and the parent of those seeds also had red flowers, those
seeds are said to be ____________________.
a. true-breeding
b. heterozygous
c. abnormal
19. In Mendel's experiments, he first cross-bred true breeding purple-flowered peas with true breeding white-flowered
peas. The first filial generation was found to consist entirely of ____________________-flowered pea plants.
a. purple
b. white
c. an intermediate color
20. Mendel found that the F1 generation in his pea plant experiments looked like only one of the original parent
plants, but that the flower color trait exhibited by the other parent showed up again in F 2. He suggested that purple
flower color was ____________________ with respect to flower color in peas.
a. recessive
b. dominant
21. When one trait usually expresses itself in conjunction with another, and the genes which control that expression
are found on the same chromosome, those two traits are genetically ____________________.
22. Sometimes, chromosomes will exchange stretches of DNA during a crossing-over event. This occurs at a
____________________.
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
23. When true breeding snapdragons with red flowers are cross-bred with true breeding white-flowered snapdragons,
the progeny exhibit a color between white and red. This is because red and white have ____________________
dominance over each other.
24. In the diagram below, the capital P stands for purple, and the small p indicates white. This is an example of
complete dominance. Label each of the F2 offspring according to their color, as indicated by their genotype.
Answer:
Label A:
Label B:
Label C:
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
25. Fill in the missing genotype for each of the eggs across the top of the Punnett square below.
Answer:
Label A:
Label B:y
Label C:
Label D:
Hint: See Figure 12-6 in the text.
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
26. Human eye color is a trait that shows incomplete or mixed dominance. Using the clues given in the Punnett
square below, complete the genotypes of the offspring on the diagonal.
Answer:
Label A:
Label B:
Label C:
Label D:
27. Which of the following can account for a situation where Mendel's Law of Independent Assortment fails to hold?
a. The genes are on the same chromosome.
b. pleiotropy
c. self-fertilization
d. The genes have undergone recombination.
e. crossing over
28. Some people are said to be "carriers" of genetic disorders. What does this mean?
a. The individual is heterozygous for the disorder, and the allele for the disorder is recessive.
b. The individual is heterozygous for the disorder, and the allele for the disorder is dominant.
c. The individual is homozygous for the disorder.
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
d. The individual is homozygous for the disorder, but is protected by the presence of an immunity
gene.
29. Which of the following is true of a man with hemophilia?
a. The man inherited the hemophilia gene from his mother.
b. The man inherited the hemophilia gene from his father.
c. The man could have inherited the hemophilia gene from either his mother or his father.
30. What happens if a baby has only one X chromosome, and no Y?
a. Such a major chromosome deficiency is lethal, so the baby would be stillborn.
b. This baby would be a female with Turner syndrome.
c. The baby would be a male with Turner syndrome.
d. The individual would have Klinefelter syndrome.
31. Which of the following is caused by an abnormal number of autosomes?
a. Down syndrome
b. Klinefelter syndrome
c. Turner syndrome
d. Marfan syndrome
32. Mendel's experiments with dihybrid crosses led him to develop his law of __________________.
33. Geneticists study patterns of inheritance in human families to learn about genetic diseases. A chart showing how
a trait is inherited over several generations of a family is called a ________________.
34. Heterozygous individuals are ______________ of recessive genetic disorders.
35. Errors in meiosis that cause a gamete to have too few or too many chromosomes are called
_________________.
36. A person with XO sex chromosomes has _______________ syndrome.
37. An organism is described as Rr:red. The Rr is the organism’s [A]; red is the organism’s [B]; and the organism is
[C].
a. [A] phenotype; [B] genotype; [C] degenerate
b. [A] karyotype; [B] hybrid; [C] recessive
c. [A] genotype; [B] phenotype; [C] heterozygous
d. [A] gamete; [B] linkage; [C] pleiotropic
e. [A] zygote; [B] phenotype; [C] homozygous
38. The 9:3:3:1 ratio is a ratio of
a. phenotypes in a test cross
b. phenotypes in a cross of individuals that differ in one trait
c. phenotypes in a cross of individuals that differ in two traits
d. genotypes in a cross of individuals that differ in one trait
e. genotypes in a cross of individuals that differ in two traits
39. A lawyer tells a male client that blood type cannot be used to his advantage in a paternity suit against the client
because the child could, in fact, be the client’s, according to blood type. Which of the following is the only possible
combination supporting this hypothetical circumstance? (Answers are in the order mother: father: child.)
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Biology: Life on Earth 7e
Student Self Test Questions and Answers
a. A:B:O
b. A:O:B
c. AB:A:O
d. AB:O:AB
e. B:O:A
40. A heterozygous red-eyed female Drosophila mated with a white-eyed male would produce
a. red-eyed females and white-eyed males in the F1
b. white-eyed females and red-eyed males in the F1
c. half red- and half white-eyed females and all white eyed males in the F1
d. all white-eyed females and half red- and half white eyed males in the F1
e. half red- and half white-eyed females as well as males in the F1
41. Which is NOT true of sickle-cell anemia?
a. It is most common in African Americans.
b. It involves a one-amino-acid change in hemoglobin.
c. It involves red blood cells.
d. It is lethal in heterozygotes because it is dominant.
e. It confers some resistance to malaria.
42. Sex-linked disorders such as color blindness and hemophilia are
a. caused by genes on the X chromosome
b. caused by genes on the autosome
c. caused by genes on the Y chromosome
d. expressed only in men
e. expressed only when two chromosomes are homozygous recessive
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