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Holt Biology Chapter 7 Test A Answer Key

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Answer Key
Chapter Test A
Multiple Choice
1.
2.
3.
4.
5.
6.
7.
b
c
d
c
c
c
a
8.
9.
10.
11.
12.
13.
14.
15.
a
d
c
c
a
d
c
b
more males than females
with the phenotype.
25. Students should draw
Punnett square with W/w at
the top and w/w at the
left side; resulting offspring
Ww, Ww, ww, ww
Copyright by McDougal Littell, a division of Houghton Mifflin Company
Short Answer
16. C2C2
17. pink
18. Parents are C1C1 and C2C2;
all offspring are C1C2.
19. 1 = C1C1, 2 = C1C2, 3 =
C1C2, 4 = C2C2; incomplete
dominance
20. Codominance. The
phenotypes of both parents
are expressed fully and
separately in the offspring.
21. a pedigree chart
22. individuals with a given
phenotype
23. The phenotype is caused by
a dominant allele because
the father has genotype
ww and does not have the
phenotype. Additionally,
the mother has genotype
Ww and has the phenotype.
24. There are more females
than males with the
phenotype. When a gene
is sex-linked, there will be
Answer Key
1
CHAPTER
7
EXTENDING MENDELIAN GENETICS
Chapter Test A
Multiple Choice
Choose the letter of the best answer. (15 credits)
1. A person who has a disorder caused by
5. For an XX female to express a recessive
a recessive allele is
sex-linked trait, she must have
a. considered a carrier of the disorder.
a. a Y chromosome.
b. homozygous for the recessive allele.
b. an inactivated allele.
c. two recessive alleles.
d. two dominant alleles.
disorder.
6. Human height occurs in a continuous
2. Gene expression is influenced by many
factors. Which of the following is a
factor in gene expression?
a. karyotype
c. environment
b. pedigree
d. phenotype
3. The Punnett square in Figure 7.1 shows
a cross between two parents who have
the genotype Ss for a genetic disorder
caused by a recessive allele. Which
of the following will have the genetic
disorder?
range because it is affected by the
interaction of several genes, making it a
a. autosomal trait.
b. sex-linked trait.
c. polygenic trait.
d. codominant trait.
7. Suppose a mouse is homozygous for
CHAPTER 7
Extending Mendelian Genetics
c. unable to pass the allele to offspring.
d. certain to have offspring with the
alleles that produce black fur and
homozygous for alleles of an epistatic
gene that prevents fur coloration. What
color fur will the mouse have?
Copyright © McDougal Littell/Houghton Mifflin Company.
a. all white
b. mostly black
c. entirely gray
d. black and white
FIG. 7.1
a. Ss parent
c. SS offspring
b. Ss offspring
d. ss offspring
4. Two parents have the genotype Gg for a
genetic disorder caused by a dominant
allele. What is the chance that any of
their children will inherit the disorder?
a. 25%
c. 75%
b. 50%
d. 100%
Assessment Book
McDougal Littell Biology
Chapter Test A
133
CHAPTER TEST A, CONTINUED
8. The gene linkage map shown in Figure
7.2 shows the order of genes A, B, and
C. Which of the following statements
about the genes is true?
8.5
C
A
FIG. 7.2
CHAPTER 7
Extending Mendelian Genetics
a. The distance between A and B is
14.5 map units.
b. A and B cross over 2.5% of the time.
c. A and C are linked 8.5% of the time.
d. B and C are most likely to be
inherited together.
9. Thomas Morgan’s research with fruit
flies determined that
a. does not have the disorder but can
pass it on
b. will develop the disorder only late
in life
c. cannot pass the disorder to sons, just
daughters
d. the allele is not passed on due to Y
chromosome inactivation
13. Some members of a family have a
recessive sex-linked disorder. Which
of the following statements about the
family would be true?
a. All males would have the disorder.
b. All females would be carriers.
a. alleles always assort independently.
c. Only males would have the disorder.
b. chromosomes are inherited as a
d. Only females would be carriers.
group.
c. genes never assort independently.
d. traits sometimes are inherited as a
group.
10. Two genes cross over 6% of the time.
This percentage means that the genes are
a. inactivated in 6 out of 100 offspring.
b. incompletely dominant in 6 out of
100 offspring.
c. not inherited together in 6 out of 100
offspring.
d. on sex chromosomes in 6 out of 100
offspring.
11. A female is born with attached earlobes,
which is a recessive phenotype. Which
of the following genotypes could her
parents have?
134
genetic disorder. Which of the following
phrases about this person is true?
a. RR and RR
c. Rr and rr
b. Rr and RR
d. RR and rr
Chapter Test A
14. What is the main reason that sex-linked
disorders are most often observed in
males?
a. The X chromosome only has genes
for genetic disorders.
b. The Y chromosome cannot have
genes that cause genetic disorders.
c. The Y chromosome cannot mask
alleles on the X chromosome.
d. The X chromosome has genes only
for sex determination.
15. Which of the following tools is used
to match up chromosome pairs using
chemical stains?
a. pedigree chart
c. meiosis map
b. karyotype
d. linkage map
Assessment Book
McDougal Littell Biology
Copyright © McDougal Littell/Houghton Mifflin Company.
B
6
12. Suppose a person is a carrier for a
CHAPTER TEST A, CONTINUED
Short Answer Use the diagram below to answer items 16–20. (5 credits)
Crosses Between
Parental Generation
Pea Plants
X
Red
White
First Generation
X
Pink
?
Second Generation
Red
C1C1
Pink
C1C2
Pink
C1C2
CHAPTER 7
Extending Mendelian Genetics
FIG. 7.3
White
C2C2
16. Write the genotypes of the pea plants in the parental generation shown in Figure 7.3.
17. What is the phenotype of the unlabeled pea plant in the first generation?
18. Use the genotypes of the parents to make a Punnett square for the first generation of
Copyright © McDougal Littell/Houghton Mifflin Company.
offspring.
19. Which type of interaction is shown by the alleles for flower color?
20. Suppose the first generation pea plants had flowers that were partly red and partly white
instead of all pink. What type of relationship between alleles would this be? Write one
statement to support your answer. Use the word phenotype in your answer.
Assessment Book
McDougal Littell Biology
Chapter Test A
135
CHAPTER TEST A, CONTINUED
Use the diagram below to answer items 21–25. (5 credits)
= male without phenotype
Ww
1
2
ww
3
= female without phenotype
4
5
CHAPTER 7
Extending Mendelian Genetics
FIG. 7.4
21. What type of chart is shown in Figure 7.4?
22. What do the shaded shapes represent?
23. The phenotype is caused by a dominant allele. Write two statements to support this fact.
25. Make a Punnett square using the parental genotypes. Find all the possible genotypes for
the offspring in the F1 generation.
136
Chapter Test A
Assessment Book
McDougal Littell Biology
Copyright © McDougal Littell/Houghton Mifflin Company.
24. The phenotype is caused by an autosomal gene. Explain why.
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