Genetics the Science of Heredity
Multiple Choice
Identify the choice that best completes the statement or answers the question.
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1. What did Gregor Mendel do to study different characteristics in his genetics experiments?
a. He studied only asexual plants.
b. He studied only tall and short pea plants.
c. He cross-pollinated plants.
d. He cross-pollinated both plants and animals.
2. In Mendel’s experiments, what proportion of the plants in the F2 generation had a trait
that had been absent in the F1 generation?
a. none
b. one fourth
c. half
d. three fourths
3. Which term refers to physical characteristics that are studied in genetics?
a. traits
b. offspring
c. generations
d. hybrids
4. Factors that control traits are called
a. genes.
b. purebreds.
c. recessives.
d. parents.
5. Scientists call an organism that has two different alleles for a trait a
a. hybrid.
b. trait.
c. purebred.
d. factor.
6. What does the notation AA mean to geneticists?
a. two dominant alleles
b. heterozygous alleles
c. at least one dominant allele
d. one dominant and one recessive allele
7. What does the notation Aa mean to geneticists?
a. two dominant alleles
b. two recessive alleles
c. homozygous alleles
d. one dominant allele and one recessive allele
8. The different forms of a gene are called
a. alleles.
b. factors.
c. masks.
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9.
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10.
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11.
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12.
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13.
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14.
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15.
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16.
d. traits.
What is probability?
a. the actual results from a series of events
b. a number that describes how likely it is that an event will occur
c. the way the results of one event affect the next event
d. the number of times a coin lands heads up
What is the probability of producing a tall pea plant from a genetic cross between two
hybrid tall pea plants?
a. one in four
b. two in four
c. three in four
d. four in four
What does a Punnett square show?
a. all the possible outcomes of a genetic cross
b. only the dominant alleles in a genetic cross
c. only the recessive alleles in a genetic cross
d. all of Mendel’s discoveries about genetic crosses
If a homozygous black guinea pig (BB) is crossed with a homozygous white guinea pig
(bb), what is the probability that an offspring will have black fur?
a. 25 percent
b. 50 percent
c. 75 percent
d. 100 percent
An organism’s physical appearance is its
a. genotype.
b. phenotype.
c. codominance.
d. heterozygous.
An organism’s genotype is its
a. genetic makeup.
b. feather color.
c. physical appearance.
d. stem height.
An organism that has two identical alleles for a trait is
a. codominant.
b. tall.
c. homozygous.
d. heterozygous.
A heterozygous organism has
a. three different alleles for a trait.
b. two identical alleles for a trait.
c. only one allele for a trait.
d. two different alleles for a trait.
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17. A purebred chicken with white feathers is crossed with a purebred chicken that has black
feathers. Each of their offspring has both black and white feathers. Why does this
happen?
a. Both alleles for feather color are dominant.
b. Both alleles for feather color are recessive.
c. The alleles for feather color are neither dominant nor recessive.
d. Several alleles work together to determine the trait.
18. What is the chromosome theory of inheritance?
a. Chromosomes are carried from parents to offspring on hybrids.
b. Genes are carried from parents to offspring on chromosomes.
c. Hybrid pairs of chromosomes combine to form offspring.
d. Codominant genes combine to form new hybrids.
19. Walter Sutton discovered that the sex cells of grasshoppers have
a. 12 times the number of chromosomes found in the body cells.
b. twice the number of chromosomes found in the body cells.
c. the same number of chromosomes found in the body cells.
d. half the number of chromosomes found in the body cells.
20. What happens during meiosis?
a. Two sex cells combine.
b. Chromosome pairs separate and are distributed into new sex cells.
c. Each sex cell copies itself to form four new chromosomes.
d. Chromosome pairs remain together when new sex cells are formed.
21. When sex cells combine to produce offspring, each sex cell will contribute
a. one fourth the number of chromosomes in body cells.
b. half the number of chromosomes in body cells.
c. the normal number of chromosomes in body cells.
d. twice the number of chromosomes in body cells.
22. Chromosomes are made up of
a. one pair of alleles.
b. many traits joined together.
c. transfer RNA.
d. many genes joined together.
23. What determines the genetic code?
a. the order of nitrogen bases along a gene
b. the number of nitrogen bases in a DNA molecule
c. the order of amino acids in a protein
d. the number of guanine and cytosine bases in a chromosome
24. The order of the bases along a gene determines the order in which
a. sugars are put together to form a carbohydrate.
b. phosphates are arranged in DNA.
c. amino acids are put together to form a protein.
d. chromosomes are arranged in the nucleus.
25. What does messenger RNA do during protein synthesis?
a. copies the coded message from the DNA and carries it into the cytoplasm
b. copies the coded message from the DNA and carries it into the nucleus
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26.
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27.
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28.
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29.
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30.
c. carries amino acids and adds them to the growing protein
d. copies the coded message from the protein and carries it into the nucleus
What do transfer RNA molecules do during protein synthesis?
a. copy the coded message from the protein and carry it into the nucleus
b. copy the coded message from the DNA and carry it into the nucleus
c. carry amino acids and add them to the growing protein
d. copy the coded message from the DNA and carry it into the cytoplasm
Where does protein synthesis take place?
a. in the ribosomes in the nucleus of the cell
b. on the ribosomes in the cytoplasm of the cell
c. in the chromosomes in the nucleus of the cell
d. on the chromosomes in the cytoplasm of the cell
Which nitrogen base in RNA is NOT part of DNA?
a. adenine
b. guanine
c. cytosine
d. uracil
What is a mutation?
a. any change that is harmful to an organism
b. any change in a gene or chromosome
c. any change that is helpful to an organism
d. any change in the phenotype of a cell
A mutation is harmful to an organism if it
a. changes the DNA of the organism.
b. changes the phenotype of the organism.
c. reduces the organism’s chances for survival and reproduction.
d. makes the organism better able to avoid predators.
Modified True/False
Indicate whether the statement is true or false. If false, change the identified word or phrase to make
the statement true.
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31. When Mendel crossed purebred short plants with purebred tall plants, all of the offspring
were short. _________________________
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32. A hybrid is the offspring of parents that have different alleles for a trait.
_________________________
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33. A pea plant that is heterozygous for tall stems has the alleles Tt.
_________________________
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34. A Punnett square shows all the possible combinations of alleles resulting from a cross.
_________________________
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35. An organism’s phenotype is its allele combinations. _________________________
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36. Chromosomes carry genes from parents to offspring. _________________________
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37. The sex cells produced by meiosis have twice the number of chromosomes as the parent
cells. _________________________
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38. The number of DNA bases along a gene specifies the type of protein that will be
produced. _________________________
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39. Transfer RNA carries coded messages from the nucleus to the cytoplasm.
_________________________
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40. A mutation in a sex cell can be passed to offspring. _________________________
Completion
Complete each statement.
41. A(n) ____________________ organism is the offspring of many generations of
organisms that have the same trait.
42. If a(n) ____________________ allele is present, its trait will appear in the organism.
43. In pea plants, the tall-stem allele and the short-stem allele are different forms of the same
____________________.
44. If D represents the dominant allele of a gene, then ____________________ represents
the recessive allele.
45. Mendel used the principles of ____________________ to predict what percent of
offspring would show a particular trait.
46. If each of ten events is equally likely to occur, the probability of each individual event
occurring is ____________________ percent.
47. A chart used to predict results of genetic crosses is known as a(n)
____________________.
48. In a cross between two hybrid Tt pea plants, ____________________ percent of the
offspring will be Tt.
49. An organism that has two dominant or two recessive alleles is said to be
____________________ for that trait.
50. Alleles that are neither dominant nor recessive produce an inheritance pattern known as
____________________.
51. Genes are carried from parents to their offspring on structures called
____________________.
52. The process in which a parent cell divides twice to produce sex cells is called
____________________.
53. If all of the sex cells of an organism have the T allele, the genotype of that organism must
be ____________________.
54. An organism can be heterozygous for some traits and ____________________ for others.
55. The chromosomes in a pair may each have different ____________________ for each
gene.
56. The genetic code is found in the order of nitrogen ____________________ along a gene.
57. A set of three bases codes for one specific ____________________ in a protein.
58. ____________________ RNA adds amino acids to a growing protein.
59. A section of DNA has the base sequence TGAG. The corresponding section of a
messenger RNA molecule will have the base sequence ___________________.
60. The substitution of one base for another during DNA replication is an example of a(n)
____________________.
Short Answer
Use the diagram to answer each question.
61. Which trait—white flowers or purple flowers—is controlled by a dominant allele? Which
is controlled by a recessive allele? How do you know?
62. In which generation are the parents purebred? In which generation are they hybrids?
63. In the F2 generation, what percent of the offspring have purple flowers? What is the
genotype of the purple-flowered offspring?
64. In the F2 generation, what percent of the offspring have white flowers? What are the
genotypes of the white-flowered offspring?
65. Suppose one of the parents of the F2 generation had been ww instead of Ww. What
percent of the offspring would have purple flowers? What percent would have white
flowers?
66. In the F1 generation, what is the genotype of the offspring? What is their phenotype?
Use the diagram to answer each question.
67. Identify structure A and state what it is made of.
68. Identify structures B and C.
69. Identify structure D and state where it is made.
70. Identify structure E and describe its function.
71. What are the three nitrogen bases in transfer RNA that pair with bases A-G-U in
messenger RNA?
72. If one of the nitrogen bases on structure D were replaced by a different base, what effect
might that have on protein synthesis?
Essay
73. Explain why Mendel’s cross of purebred tall and short pea plants resulted in only tall
plants.
74. In pea plants, green pod color is controlled by a dominant allele. Yellow is controlled by
a recessive allele. Explain why a plant with yellow pods can never be a hybrid.
75. A woman gives birth to a son. Two years later, she gives birth to another son. What is the
probability that her third child will be a girl? Explain your reasoning.
76. In pea plants, the allele for smooth pods (S) is dominant over the allele for pinched pods
(s). Construct a Punnett square that shows a cross between an SS plant and an Ss plant.
Predict what percent of the offspring are likely to have smooth pods.
77. Some clover plants have leaves with a white stripe. Other clover plants have leaves with a
white spot. When these two types of plants are crossed, the leaves of the offspring have a
white stripe and a white spot. Explain how this inheritance pattern occurs.
78. Explain the function of meiosis.
79. Describe what messenger RNA and transfer RNA do during protein synthesis.
80. Contrast the effects of harmful and helpful mutations.
Genetics the Science of Heredity
Answer Section
MULTIPLE CHOICE
1. ANS: C
PTS: 1
DIF: L2
OBJ: CaLS.5.1.1 Describe the results of Mendel's experiments. STA: S 7.2.d
BLM: comprehension
2. ANS: B
PTS: 1
DIF: L2
OBJ: CaLS.5.1.1 Describe the results of Mendel's experiments. STA: S 7.2.d
BLM: comprehension
3. ANS: A
PTS: 1
DIF: L1
OBJ: CaLS.5.1.1 Describe the results of Mendel's experiments. STA: S 7.2.d
BLM: knowledge
4. ANS: A
PTS: 1
DIF: L1
OBJ: CaLS.5.1.2 Identify what controls the inheritance of traits in organisms.
STA: S 7.2.d
BLM: knowledge
5. ANS: A
PTS: 1
DIF: L1
OBJ: CaLS.5.1.2 Identify what controls the inheritance of traits in organisms.
STA: S 7.2.d
BLM: knowledge
6. ANS: A
PTS: 1
DIF: L2
OBJ: CaLS.5.1.2 Identify what controls the inheritance of traits in organisms.
STA: S 7.2.d
BLM: application
7. ANS: D
PTS: 1
DIF: L2
OBJ: CaLS.5.1.2 Identify what controls the inheritance of traits in organisms.
STA: S 7.2.d
BLM: application
8. ANS: A
PTS: 1
DIF: L1
OBJ: CaLS.5.1.2 Identify what controls the inheritance of traits in organisms.
STA: S 7.2.d
BLM: knowledge
9. ANS: B
PTS: 1
DIF: L1
OBJ: CaLS.5.2.1 Define probability and describe how it helps explain the results of
genetic crosses.
STA: S 7.2.b
BLM: knowledge
10. ANS: C
PTS: 1
DIF: L2
OBJ: CaLS.5.2.1 Define probability and describe how it helps explain the results of
genetic crosses.
STA: S 7.2.d
BLM: analysis
11. ANS: A
PTS: 1
DIF: L1
OBJ: CaLS.5.2.1 Define probability and describe how it helps explain the results of
genetic crosses.
STA: S 7.2.d
BLM: knowledge
12. ANS: D
PTS: 1
DIF: L2
OBJ: CaLS.5.2.1 Define probability and describe how it helps explain the results of
genetic crosses.
STA: S 7.2.d
BLM: analysis
13. ANS: B
PTS: 1
DIF: L1
OBJ: CaLS.5.2.2 Explain what is meant by genotype and phenotype.
STA: S 7.2.d
BLM: knowledge
14. ANS:
OBJ:
STA:
15. ANS:
OBJ:
STA:
16. ANS:
OBJ:
STA:
17. ANS:
OBJ:
BLM:
18. ANS:
OBJ:
STA:
19. ANS:
OBJ:
STA:
20. ANS:
OBJ:
BLM:
21. ANS:
OBJ:
BLM:
22. ANS:
OBJ:
STA:
23. ANS:
OBJ:
BLM:
24. ANS:
OBJ:
BLM:
25. ANS:
OBJ:
BLM:
26. ANS:
OBJ:
BLM:
27. ANS:
OBJ:
BLM:
28. ANS:
OBJ:
BLM:
A
PTS: 1
DIF: L1
CaLS.5.2.2 Explain what is meant by genotype and phenotype.
S 7.2.d
BLM: knowledge
C
PTS: 1
DIF: L1
CaLS.5.2.2 Explain what is meant by genotype and phenotype.
S 7.2.d
BLM: knowledge
D
PTS: 1
DIF: L1
CaLS.5.2.2 Explain what is meant by genotype and phenotype.
S 7.2.d
BLM: knowledge
C
PTS: 1
DIF: L2
CaLS.5.2.3 Tell what codominance is.
STA: S 7.2.d
comprehension
B
PTS: 1
DIF: L1
CaLS.5.3.1 Describe the role chromosomes play in inheritance.
S 7.2.b
BLM: knowledge
D
PTS: 1
DIF: L2
CaLS.5.3.1 Describe the role chromosomes play in inheritance.
S 7.2.b
BLM: comprehension
B
PTS: 1
DIF: L1
CaLS.5.3.2 Identify the events that occur during meiosis. STA: S 7.2.b
knowledge
B
PTS: 1
DIF: L2
CaLS.5.3.2 Identify the events that occur during meiosis. STA: S 7.2.b
comprehension
D
PTS: 1
DIF: L1
CaLS.5.3.3 Explain the relationship between chromosomes and genes.
S 7.2.b
BLM: knowledge
A
PTS: 1
DIF: L1
CaLS.5.4.1 Explain what forms the genetic code.
STA: S 7.1.a
knowledge
C
PTS: 1
DIF: L2
CaLS.5.4.1 Explain what forms the genetic code.
STA: S 7.1.a
comprehension
A
PTS: 1
DIF: L1
CaLS.5.4.2 Describe how a cell produces proteins.
STA: S 7.1.a
knowledge
C
PTS: 1
DIF: L2
CaLS.5.4.2 Describe how a cell produces proteins.
STA: S 7.1.a
comprehension
B
PTS: 1
DIF: L2
CaLS.5.4.2 Describe how a cell produces proteins.
STA: S 7.1.a
comprehension
D
PTS: 1
DIF: L2
CaLS.5.4.2 Describe how a cell produces proteins.
STA: S 7.1.a
comprehension
29. ANS:
OBJ:
STA:
30. ANS:
OBJ:
STA:
B
PTS: 1
DIF: L1
CaLS.5.4.3 Identify how mutations can affect an organism.
S 7.1.a
BLM: knowledge
C
PTS: 1
DIF: L2
CaLS.5.4.3 Identify how mutations can affect an organism.
S 7.1.a
BLM: comprehension
MODIFIED TRUE/FALSE
31. ANS: F, tall
32.
33.
34.
35.
PTS: 1
DIF: L1
OBJ: CaLS.5.1.1 Describe the results of Mendel's experiments. STA: S 7.2.d
BLM: knowledge
ANS: T
PTS: 1
DIF: L1
OBJ: CaLS.5.1.2 Identify what controls the inheritance of traits in organisms.
STA: S 7.2.d
BLM: knowledge
ANS: T
PTS: 1
DIF: L2
OBJ: CaLS.5.1.2 Identify what controls the inheritance of traits in organisms.
STA: S 7.2.d
BLM: application
ANS: T
PTS: 1
DIF: L1
OBJ: CaLS.5.2.1 Define probability and describe how it helps explain the results of
genetic crosses.
STA: S 7.2.d
BLM: knowledge
ANS: F, genotype
PTS:
OBJ:
STA:
36. ANS:
OBJ:
STA:
37. ANS:
1
DIF: L1
CaLS.5.2.2 Explain what is meant by genotype and phenotype.
S 7.2.d
BLM: knowledge
T
PTS: 1
DIF:
CaLS.5.3.1 Describe the role chromosomes play in inheritance.
S 7.2.b
BLM: knowledge
F, half
PTS:
OBJ:
BLM:
38. ANS:
1
DIF: L2
CaLS.5.3.2 Identify the events that occur during meiosis. STA: S 7.2.b
comprehension
F, order
PTS:
OBJ:
BLM:
39. ANS:
1
DIF: L2
CaLS.5.4.1 Explain what forms the genetic code.
comprehension
F, Messenger
PTS: 1
DIF: L1
OBJ: CaLS.5.4.2 Describe how a cell produces proteins.
L1
STA: S 7.1.a
STA: S 7.1.a
BLM:
40. ANS:
OBJ:
STA:
knowledge
T
PTS: 1
DIF:
CaLS.5.4.3 Identify how mutations can affect an organism.
S 7.2.b
BLM: application
L2
COMPLETION
41. ANS: purebred
PTS:
OBJ:
BLM:
42. ANS:
1
DIF: L1
CaLS.5.1.1 Describe the results of Mendel's experiments. STA: S 7.2.d
knowledge
dominant
PTS:
OBJ:
STA:
43. ANS:
1
DIF: L2
CaLS.5.1.2 Identify what controls the inheritance of traits in organisms.
S 7.2.d
BLM: comprehension
gene
PTS:
OBJ:
STA:
44. ANS:
1
DIF: L2
CaLS.5.1.2 Identify what controls the inheritance of traits in organisms.
S 7.2.d
BLM: comprehension
d
PTS:
OBJ:
STA:
45. ANS:
1
DIF: L2
CaLS.5.1.2 Identify what controls the inheritance of traits in organisms.
S 7.2.d
BLM: application
probability
PTS: 1
DIF: L2
OBJ: CaLS.5.2.1 Define probability and describe how it helps explain the results of
genetic crosses.
STA: S 7.2.b
BLM: comprehension
46. ANS:
10
ten
PTS: 1
DIF: L2
OBJ: CaLS.5.2.1 Define probability and describe how it helps explain the results of
genetic crosses.
STA: S 7.2.b
BLM: analysis
47. ANS: Punnett square
PTS: 1
DIF: L1
OBJ: CaLS.5.2.1 Define probability and describe how it helps explain the results of
genetic crosses.
STA: S 7.2.d
BLM: knowledge
48. ANS:
50
fifty
PTS: 1
DIF: L2
OBJ: CaLS.5.2.1 Define probability and describe how it helps explain the results of
genetic crosses.
STA: S 7.2.d
BLM: analysis
49. ANS: homozygous
PTS:
OBJ:
STA:
50. ANS:
1
DIF: L1
CaLS.5.2.2 Explain what is meant by genotype and phenotype.
S 7.2.d
BLM: knowledge
codominance
PTS: 1
DIF: L1
is.
STA: S 7.2.d
BLM: knowledge
51. ANS: chromosomes
OBJ: CaLS.5.2.3 Tell what codominance
PTS:
OBJ:
STA:
52. ANS:
1
DIF: L1
CaLS.5.3.1 Describe the role chromosomes play in inheritance.
S 7.2.b
BLM: knowledge
meiosis
PTS:
OBJ:
BLM:
53. ANS:
1
DIF: L1
CaLS.5.3.2 Identify the events that occur during meiosis. STA: S 7.2.b
knowledge
TT
PTS:
OBJ:
BLM:
54. ANS:
1
DIF: L2
CaLS.5.3.2 Identify the events that occur during meiosis. STA: S 7.2.b
application
homozygous
PTS:
OBJ:
STA:
55. ANS:
1
DIF: L2
CaLS.5.3.3 Explain the relationship between chromosomes and genes.
S 7.2.b
BLM: application
alleles
PTS:
OBJ:
STA:
56. ANS:
1
DIF: L2
CaLS.5.3.3 Explain the relationship between chromosomes and genes.
S 7.2.b
BLM: comprehension
bases
PTS: 1
DIF: L1
OBJ: CaLS.5.4.1 Explain what forms the genetic code.
BLM: knowledge
STA: S 7.2.e
57. ANS: amino acid
PTS:
OBJ:
BLM:
58. ANS:
1
DIF: L2
CaLS.5.4.1 Explain what forms the genetic code.
comprehension
Transfer
PTS:
OBJ:
BLM:
59. ANS:
1
DIF: L1
CaLS.5.4.2 Describe how a cell produces proteins.
knowledge
ACUC
PTS:
OBJ:
BLM:
60. ANS:
1
DIF: L2
CaLS.5.4.2 Describe how a cell produces proteins.
application
mutation
STA: S 7.1.a
STA: S 7.1.a
STA: S 7.2.e
PTS: 1
DIF: L2
OBJ: CaLS.5.4.3 Identify how mutations can affect an organism.
STA: S 7.2.e
BLM: application
SHORT ANSWER
61. ANS:
White flowers are controlled by a dominant allele. Purple flowers are controlled by a
recessive allele. Dominant alleles are represented by capital letters, and recessive alleles
are represented by the lowercase versions of the same letters.
PTS: 1
DIF: L2
OBJ: CaLS.5.1.2 Identify what controls the inheritance of traits in organisms.
STA: S 7.2.d
BLM: application
62. ANS:
The parents in the F1 generation are purebred. The parents in the F2 generation are
hybrids.
PTS: 1
DIF: L2
OBJ: CaLS.5.1.2 Identify what controls the inheritance of traits in organisms.
STA: S 7.2.b
BLM: application
63. ANS:
In the F2 generation, 25% of the offspring have purple flowers. Their genotype is ww.
PTS: 1
DIF: L2
OBJ: CaLS.5.2.1 Define probability and describe how it helps explain the results of
genetic crosses.
STA: S 7.2.d
BLM: analysis
64. ANS:
In the F2 generation, 75% of the offspring have white flowers. Their genotypes are WW
and Ww.
PTS: 1
DIF: L2
OBJ: CaLS.5.2.1 Define probability and describe how it helps explain the results of
genetic crosses.
STA: S 7.2.d
BLM: analysis
65. ANS:
If one of the parents had been ww, 50% of the offspring would have purple flowers and
50% would have white flowers.
PTS: 1
DIF: L3
OBJ: CaLS.5.2.1 Define probability and describe how it helps explain the results of
genetic crosses.
STA: S 7.2.d
BLM: synthesis
66. ANS:
The genotype is Ww. The phenotype is white flowers.
PTS: 1
DIF: L2
OBJ: CaLS.5.2.2 Explain what is meant by genotype and phenotype.
STA: S 7.2.d
BLM: application
67. ANS:
A is a protein. It is made of amino acids.
PTS: 1
DIF: L2
OBJ: CaLS.5.4.2 Describe how a cell produces proteins.
BLM: application
68. ANS:
B is an amino acid. C is a transfer RNA molecule.
PTS: 1
DIF: L2
OBJ: CaLS.5.4.2 Describe how a cell produces proteins.
BLM: application
69. ANS:
D is a messenger RNA molecule. It is made in the nucleus.
PTS: 1
DIF: L2
OBJ: CaLS.5.4.2 Describe how a cell produces proteins.
BLM: application
70. ANS:
E is a ribosome. It is the site where proteins are made.
PTS: 1
DIF: L2
OBJ: CaLS.5.4.2 Describe how a cell produces proteins.
BLM: application
71. ANS:
The bases that pair with A-G-U are U-C-A.
STA: S 7.1.a
STA: S 7.1.a
STA: S 7.1.a
STA: S 7.1.a
PTS: 1
DIF: L2
OBJ: CaLS.5.4.2 Describe how a cell produces proteins.
STA: S 7.1.a
BLM: application
72. ANS:
A different amino acid might be produced, which might affect the structure and function
of the protein.
PTS: 1
DIF: L2
OBJ: CaLS.5.4.3 Identify how mutations can affect an organism.
STA: S 7.1.a
BLM: application
ESSAY
73. ANS:
Each of the offspring inherited an allele for height from each parent. Each offspring had
one allele for tall stems and one allele for short stems. The allele for tall stems is
dominant. Since each offspring inherited a dominant allele for tall stems, each plant had
tall stems.
PTS: 1
DIF: L3
OBJ: CaLS.5.1.1 Describe the results of Mendel's experiments. STA: S 7.2.d
BLM: synthesis
74. ANS:
Because the allele for yellow is recessive, plants with yellow pods must have two
recessive alleles. A hybrid would have one dominant allele and one recessive allele, and
would therefore be green.
PTS: 1
DIF: L2
OBJ: CaLS.5.1.2 Identify what controls the inheritance of traits in organisms.
STA: S 7.2.d
BLM: application
75. ANS:
The probability is 1 in 2, or 50 percent. The two possible results—having a boy or having
a girl—are equally likely with each birth. Because each birth is an independent event, the
probability that one result will occur does not depend on previous births.
PTS: 1
DIF: L3
OBJ: CaLS.5.2.1 Define probability and describe how it helps explain the results of
genetic crosses.
STA: S 7.2.d
BLM: synthesis
76. ANS:
S and S should be written at the top of the Punnett square, and S and s should be written
down the left side (or vice versa). Two of the boxes in the square should have SS and two
should have Ss. All of the offspring (100%) will have smooth pods.
PTS: 1
DIF: L3
OBJ: CaLS.5.2.1 Define probability and describe how it helps explain the results of
genetic crosses.
STA: S 7.2.d
BLM: synthesis
77. ANS:
The alleles that produce a white stripe and a white spot are codominant. When both
alleles are present in a plant, neither masks the other. Both traits are visible in the plant.
PTS: 1
DIF: L3
OBJ: CaLS.5.2.3 Tell what codominance
is.
STA: S 7.2.d
BLM: synthesis
78. ANS:
Meiosis ensures that each sex cell gets half the number of chromosomes in a body cell. If
meiosis did not occur, the sperm cell and the egg cell would each have the same number
of chromosomes as a body cell. When the two cells combined, the offspring would have
twice the normal number of chromosomes.
PTS: 1
DIF: L2
OBJ: CaLS.5.3.2 Identify the events that occur during meiosis. STA: S 7.2.b
BLM: analysis
79. ANS:
Messenger RNA copies the coded message from the DNA in the nucleus and carries the
message into the cytoplasm. Transfer RNA carries amino acids and adds them to the
growing protein.
PTS: 1
DIF: L2
OBJ: CaLS.5.4.2 Describe how a cell produces proteins.
STA: S 7.2.e
BLM: comprehension
80. ANS:
A harmful mutation reduces the organism’s chances for survival and reproduction. A
helpful mutation increases an organism’s chances for survival and reproduction.
PTS: 1
DIF: L3
OBJ: CaLS.5.4.3 Identify how mutations can affect an organism.
STA: S 7.1.a
BLM: analysis