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CAMPBELL BIOLOGY IN FOCUS
Urry • Cain • Wasserman • Minorsky • Jackson • Reece
11
Mendel and
the Gene Idea
Questions prepared by
Brad Stith, University of Colorado Denver
Janet Lanza, University of Arkansas at Little Rock
Louise Paquin, McDaniel College
© 2014 Pearson Education, Inc.
Imagine crossing a pea heterozygous at the loci for flower
color (white versus purple) and seed color (yellow versus
green) with a second pea homozygous for flower color (white)
and seed color (yellow). What types of gametes will the first
pea produce?
A. two gamete types: white/white and purple/purple
B. two gamete types: white/yellow and purple/green
C. four gamete types: white/yellow, white/green,
purple/yellow, and purple/green
D. four gamete types: white/purple, yellow/green,
white/white, and purple/purple
E. one gamete type: white/purple/yellow/green
© 2014 Pearson Education, Inc.
Imagine crossing a pea heterozygous at the loci for flower
color (white versus purple) and seed color (yellow versus
green) with a second pea homozygous for flower color (white)
and seed color (yellow). What types of gametes will the first
pea produce?
A. two gamete types: white/white and purple/purple
B. two gamete types: white/yellow and purple/green
C. four gamete types: white/yellow, white/green,
purple/yellow, and purple/green
D. four gamete types: white/purple, yellow/green,
white/white, and purple/purple
E. one gamete type: white/purple/yellow/green
© 2014 Pearson Education, Inc.
Pea plants were particularly well suited for use in Mendel’s
breeding experiments for all of the following reasons
except that
A. peas show easily observed variations in a number of
characters, such as pea shape and flower color.
B. it is possible to control matings between different pea
plants.
C. it is possible to obtain large numbers of progeny from
any given cross.
D. peas have an unusually long generation time.
E. many of the observable characters that vary in pea
plants are controlled by single genes.
© 2014 Pearson Education, Inc.
Pea plants were particularly well suited for use in Mendel’s
breeding experiments for all of the following reasons
except that
A. peas show easily observed variations in a number of
characters, such as pea shape and flower color.
B. it is possible to control matings between different pea
plants.
C. it is possible to obtain large numbers of progeny from
any given cross.
D. peas have an unusually long generation time.
E. many of the observable characters that vary in pea
plants are controlled by single genes.
© 2014 Pearson Education, Inc.
A cross between homozygous purple-flowered and
homozygous white-flowered pea plants results in
offspring with purple flowers. This demonstrates
A. the blending model of genetics.
B. true breeding.
C. dominance.
D. a dihybrid cross.
E. the mistakes made by Mendel.
© 2014 Pearson Education, Inc.
A cross between homozygous purple-flowered and
homozygous white-flowered pea plants results in
offspring with purple flowers. This demonstrates
A. the blending model of genetics.
B. true breeding.
C. dominance.
D. a dihybrid cross.
E. the mistakes made by Mendel.
© 2014 Pearson Education, Inc.
Imagine a genetic counselor working with a couple who have just had a child
who is suffering from Tay-Sachs disease. Neither parent has Tay-Sachs, nor
does anyone in their families. Which of the following statements should this
counselor make to this couple?
A.
“Because no one in either of your families has Tay-Sachs, you are not
likely to have another baby with Tay-Sachs. You can safely have another
child.”
B.
“Because you have had one child with Tay-Sachs, you must each carry
the allele. Any child you have has a 50% chance of having the disease.”
C. “Because you have had one child with Tay-Sachs, you must each
carry the allele. Any child you have has a 25% chance of having the
disease.”
D. “Because you have had one child with Tay-Sachs, you must both carry
the allele. However, since the chance of having an affected child is 25%,
you may safely have thee more children without worrying about having
another child with Tay-Sachs.”
E.
“You must both be tested to see who is a carrier of the Tay-Sachs allele.”
© 2014 Pearson Education, Inc.
Imagine a genetic counselor working with a couple who have just had a child
who is suffering from Tay-Sachs disease. Neither parent has Tay-Sachs, nor
does anyone in their families. Which of the following statements should this
counselor make to this couple?
A.
“Because no one in either of your families has Tay-Sachs, you are not
likely to have another baby with Tay-Sachs. You can safely have another
child.”
B.
“Because you have had one child with Tay-Sachs, you must each carry
the allele. Any child you have has a 50% chance of having the disease.”
C. “Because you have had one child with Tay-Sachs, you must each
carry the allele. Any child you have has a 25% chance of having the
disease.”
D. “Because you have had one child with Tay-Sachs, you must both carry
the allele. However, since the chance of having an affected child is 25%,
you may safely have thee more children without worrying about having
another child with Tay-Sachs.”
E.
“You must both be tested to see who is a carrier of the Tay-Sachs allele.”
© 2014 Pearson Education, Inc.
Albinism in humans occurs when both alleles at a locus
produce defective enzymes in the biochemical pathway
leading to melanin. Given that heterozygotes are normally
pigmented, which of the following statements is/are correct?
A. One normal allele produces as much melanin as two
normal alleles.
B. Each defective allele produces a little bit of melanin.
C. Two normal alleles are needed for normal melanin
production.
D. The two alleles are codominant.
E. The amount of sunlight will not affect skin color of
heterozygotes.
© 2014 Pearson Education, Inc.
Albinism in humans occurs when both alleles at a locus
produce defective enzymes in the biochemical pathway
leading to melanin. Given that heterozygotes are normally
pigmented, which of the following statements is/are correct?
A. One normal allele produces as much melanin as two
normal alleles.
B. Each defective allele produces a little bit of melanin.
C. Two normal alleles are needed for normal melanin
production.
D. The two alleles are codominant.
E. The amount of sunlight will not affect skin color of
heterozygotes.
© 2014 Pearson Education, Inc.
Imagine that the last step in a biochemical pathway to the red skin pigment of
an apple is catalyzed by enzyme X, which changes compound C to compound
D. If an effective enzyme is present, compound D is formed and the apple skin
is red. However, if the enzyme is not effective, only compound C is present
and the skin is yellow. Thinking about enzyme action, what can you accurately
say about a heterozygote with one allele for an effective enzyme X and one
allele for an ineffective enzyme X?
A.
The phenotype will probably be yellow
but cannot be red.
B.
The phenotype will probably be red
but cannot be yellow.
C. The phenotype will be a yellowish red.
D. The phenotype will be either yellow or red.
E.
The phenotype will be either yellowish
red or red.
© 2014 Pearson Education, Inc.
Imagine that the last step in a biochemical pathway to the red skin pigment of
an apple is catalyzed by enzyme X, which changes compound C to compound
D. If an effective enzyme is present, compound D is formed and the apple skin
is red. However, if the enzyme is not effective, only compound C is present
and the skin is yellow. Thinking about enzyme action, what can you accurately
say about a heterozygote with one allele for an effective enzyme X and one
allele for an ineffective enzyme X?
A.
The phenotype will probably be yellow
but cannot be red.
B.
The phenotype will probably be red
but cannot be yellow.
C. The phenotype will be a yellowish red.
D. The phenotype will be either yellow or red.
E.
The phenotype will be either yellowish
red or red.
© 2014 Pearson Education, Inc.
In humans, alleles for dark hair are genetically dominant, while
alleles for light hair are recessive. Which of the following
statements is/are most likely to be correct?
A. Dark hair alleles are more common than light hair alleles in
all areas of Europe.
B. Dark hair alleles are more common than light hair alleles
in southern Europe but not in northern Europe.
C. Dark hair alleles are equally common in all parts of Europe.
D. Dark hair is dominant to light hair in southern Europe but
recessive to light hair in northern Europe.
E. Dark hair is dominant to light hair in northern Europe but
recessive to light hair in southern Europe.
© 2014 Pearson Education, Inc.
In humans, alleles for dark hair are genetically dominant, while
alleles for light hair are recessive. Which of the following
statements is/are most likely to be correct?
A. Dark hair alleles are more common than light hair alleles in
all areas of Europe.
B. Dark hair alleles are more common than light hair alleles
in southern Europe but not in northern Europe.
C. Dark hair alleles are equally common in all parts of Europe.
D. Dark hair is dominant to light hair in southern Europe but
recessive to light hair in northern Europe.
E. Dark hair is dominant to light hair in northern Europe but
recessive to light hair in southern Europe.
© 2014 Pearson Education, Inc.
Imagine a locus with four different alleles for fur color in
an animal. The alleles are named Da, Db, Dc, and Dd. If
you crossed two heterozygotes, DaDb and DcDd, what
genotype proportions would you expect in the offspring?
A. 25% DaDc, 25% DaDd, 25% DbDc, 25% DbDd
B. 50% DaDb, 50% DcDd
C. 25% DaDa, 25% DbDb, 25% DcDc, 25% DdDdDcDd
D. 50% DaDc, 50% DbDd
E. 25% DaDb, 25% DcDd, 25% DcDc, 25% DdDd
© 2014 Pearson Education, Inc.
Imagine a locus with four different alleles for fur color in
an animal. The alleles are named Da, Db, Dc, and Dd. If
you crossed two heterozygotes, DaDb and DcDd, what
genotype proportions would you expect in the offspring?
A. 25% DaDc, 25% DaDd, 25% DbDc, 25% DbDd
B. 50% DaDb, 50% DcDd
C. 25% DaDa, 25% DbDb, 25% DcDc, 25% DdDdDcDd
D. 50% DaDc, 50% DbDd
E. 25% DaDb, 25% DcDd, 25% DcDc, 25% DdDd
© 2014 Pearson Education, Inc.
Imagine a family with two parents who both maintain
low fat levels through a combination of aerobic activity
and weight training. Which of the following statements
is/are most likely to apply to their two children?
A. The parents’ fat levels are irrelevant to the fat levels
of the children.
B. One child is likely to have low fat levels but the other
is more likely to have high fat levels because of
independent assortment of genes.
C. The children may not have the same fat levels as
their parents because genes independently assort
during meiosis.
© 2014 Pearson Education, Inc.
Envision a family in which the grandfather, age 47, has just
been diagnosed with Huntington’s disease, which is caused
by a dominant allele (and the father is a heterozygote). His
daughter, age 25, now has a 2-year-old son. No one else in
the family has the disease. What is the probability that the
daughter will contract the disease?
A. 0%
B. 25%
C. 50%
D. 75%
E. 100%
© 2014 Pearson Education, Inc.
Envision a family in which the grandfather, age 47, has just
been diagnosed with Huntington’s disease, which is caused
by a dominant allele (and the father is a heterozygote). His
daughter, age 25, now has a 2-year-old son. No one else in
the family has the disease. What is the probability that the
daughter will contract the disease?
A. 0%
B. 25%
C. 50%
D. 75%
E. 100%
© 2014 Pearson Education, Inc.
Review the family described in the previous
question. What is the probability that the baby will
contract the disease?
A. 0%
B. 25%
C. 50%
D. 75%
E. 100%
© 2014 Pearson Education, Inc.
Review the family described in the previous
question. What is the probability that the baby will
contract the disease?
A. 0%
B. 25%
C. 50%
D. 75%
E. 100%
© 2014 Pearson Education, Inc.
Imagine that you are the daughter in the family
described in the previous questions. You had been
planning on having a second child. What kind of
choices would you make about genetic testing, for
yourself and for your child?
© 2014 Pearson Education, Inc.
When a disease is said to have a multifactorial
basis, it means that
A. both genetic and environmental factors
contribute to the disease.
B. it is caused by a gene with a large number of
alleles.
C. it affects a large number of people.
D. it has many different symptoms.
E. it tends to skip a generation.
© 2014 Pearson Education, Inc.
When a disease is said to have a multifactorial
basis, it means that
A. both genetic and environmental factors
contribute to the disease.
B. it is caused by a gene with a large number of
alleles.
C. it affects a large number of people.
D. it has many different symptoms.
E. it tends to skip a generation.
© 2014 Pearson Education, Inc.