Name
Practice Test
Genetics Unit
Date
AP Biology
Choose the best answer for each question. You many want to write your
answers on a separate sheet of paper so that you can re-do this test at a later
time.
1. What do we mean when we use the terms monohybrid cross and dihybrid cross?
A) A monohybrid cross involves a single parent, whereas a dihybrid cross
involves two parents.
B) A monohybrid cross produces a single progeny, whereas a dihybrid cross
produces two progeny.
C) A dihybrid cross involves organisms that are heterozygous for two characters,
and a monohybrid cross involves only one.
D) A monohybrid cross is performed for one generation, whereas a dihybrid cross
is performed for two generations.
E) A monohybrid cross results in a 9:3:3:1 ratio, whereas a dihybrid cross gives a
3:1 ratio.
2. How many genetically unique gametes could be produced through independent
assortment by an individual with the genotype AaBbCCDdEEFf ?
A) 4
B) 8
C) 16
D) 32
E) 64
3. Which of the following differentiates between independent assortment and
segregation?
A) The law of independent assortment requires describing two or more genes
relative to one another.
B) The law of segregation requires describing two or more genes relative to one
another.
C) The law of segregation requires having two or more generations to describe.
D) The law of independent assortment is accounted for by observations of
prophase I.
E) The law of segregation is accounted for by anaphase of mitosis.
4. Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait.
What does this suggest?
A) that the parents were true-breeding for contrasting traits
B) that the trait shows incomplete dominance
C) that a blending of traits has occurred
D) that the parents were both heterozygous for a single trait
E) that each offspring has the same alleles for each of two traits
5. A sexually reproducing animal has two unlinked genes, one for fur color (F) and
one for tail length (T). Its genotype is FfTt. Which of the following genotypes is
possible in a gamete from this organism?
A) tt
B) Ff
C) FfTt
D) T
E) FT
6. Mendel accounted for the observation that traits that had disappeared in the F1
generation reappeared in the F2 generation by proposing that
A) new mutations were frequently generated in the F2 progeny, "reinventing"
traits that had been lost in the F1.
B) the mechanism controlling the appearance of traits was different between the
F1 and the F2 plants.
C) traits can be dominant or recessive, and the recessive traits were obscured by
the dominant ones in the F1.
D) the traits were lost in the F1 due to dominance of the parental traits.
E) members of the F1 generation had only one allele for each trait, but members
of the F2 had two alleles for each trait.
7. Mendel's observation of the segregation of alleles in gamete formation has its
basis in which of the following phases of cell division?
A) prophase I of meiosis
B) anaphase II of meiosis
C) metaphase I of meiosis
D) anaphase I of meiosis
E) anaphase of mitosis
8. Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to
long tails (t). What fraction of the progeny of crosses BbTt × BBtt will be
expected to have black fur and long tails?
A) 1/16
B) 3/16
C) 3/8
D) 1/2
E) 9/16
9. In the cross AaBbCc × AaBbCc, what is the probability of producing the genotype
AABBCC?
A) 1/4
B) 1/8
C) 1/16
D) 1/32
E) 1/64
10. In cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous
(Rr) offspring of red (RR) and white (rr) homozygotes. Which of the following
crosses would produce offspring in the ratio of 4 roan: 0 red: 0 white?
A) red × white
B) roan × roan
C) white × roan
D) red × roan
E) The answer cannot be determined from the information provided.
11. Which of the following is an example of polygenic inheritance?
A) pink flowers in snapdragons
B) the ABO blood group in humans
C) Huntington's disease in humans
D) white and purple flower color in peas
E) skin pigmentation in humans
12. Environmental factors can affect the expression of genes. This is best shown by
which of the following examples?
a. hydrangea plants can express different colored petals depending on soil pH
b. X-linked recessive alleles like colorblindness are passed on only from a mother
c. many genes contribute to one’s height phenotype
d. the gene for sickle cell anemia can manifest itself in multiple ways
13. Which of the following provides an example of epistasis?
A) Recessive genotypes for each of two genes (aabb) result in an albino corn
snake.
B) The allele b17 produces a dominant phenotype, although b1 through b16 do
not.
C) In rabbits and many other mammals, one genotype (ee) prevents fur color
genes from being expressed.
D) In Drosophila (fruit flies), white eyes can be due to an X-linked gene or to a
combination of other genes.
E) In cacti, there are several genes for the type of spines.
14. One of two major forms of a human condition called neurofibromatosis (NF 1) is
inherited as a dominant gene, although it may range from mildly to very severely
expressed. If a young child is the first in her family to be diagnosed, which of the
following is the best explanation?
A) The mother carries the gene but does not express it at all.
B) One of the parents has very mild expression of the gene.
C) The condition skipped a generation in the family.
D) The child has a different allele of the gene than the parents.
The following questions refer to the pedigree chart in Figure 11.2 for a family, some of
whose members exhibit the dominant trait, W. Affected individuals are indicated by a
dark square or circle.
Fig. 11.2
15. What is the genotype of individual II-5?
A) WW
B) Ww
C) ww
D) WW or ww
E) ww or Ww
16. What is the likelihood that the progeny of IV-3 and IV-4 will have the trait?
A) 0%
B) 25%
C) 50%
D) 75%
E) 100%
17. Two true-breeding stocks of pea plants are crossed. One parent has red, axial
flowers and the other has white, terminal flowers; all F1 individuals have red,
axial flowers. The genes for flower color and location assort independently.
If 1,000 F2 offspring (F1 X F1) resulted from the cross, approximately how many
of them would you expect to have red, terminal flowers?
A) 65
B) 190
C) 250
D) 565
E) 750
18. Tallness (T) in snapdragons is dominant to dwarfness (t), and red (R) flower color
is dominant to white (r). The heterozygous condition results in pink (Rr) flower
color
A homozygous tall, red snapdragon is crossed with a dwarf plant and white
flowers. What are the genotypes and phenotypes of the F1 individuals?
A) TtRr–tall and red
B) ttrr–dwarf and white
C) ttRr–dwarf and pink
D) TtRr–tall and pink
E) TTRR–tall and red
19. A man is brought to a paternity case. His blood type is found to be blood type B.
His alleged son’s blood type is blood type O and the woman who is claiming that
he is the father has blood type A. Using additional DNA evidence, the man is, in
fact, found to be the father. What must his genotype of blood type be? _____
20. In cats, black fur color is caused by an X-linked allele; the other allele at this
locus causes orange color. The heterozygote is tortoiseshell. What kinds of
offspring would you expect from the cross of a black female and an orange male?
A) tortoiseshell females; tortoiseshell males
B) black females; orange males
C) orange females; orange males
D) tortoiseshell females; black males
E) orange females; black males
21. Cinnabar eyes is a sex-linked recessive characteristic in fruit flies. If a female
having cinnabar eyes is crossed with a wild-type male, what percentage of the F1
males will have cinnabar eyes?
A) 0%
B) 25%
C) 50%
D) 75%
E) 100%
22. Sex determination in mammals is due to the SRY region of the Y chromosome.
An abnormality of this region could allow which of the following to have a male
phenotype?
A) Turner syndrome, 45, X
B) translocation of SRY to an autosome of a 46, XX individual
C) a person with an extra X chromosome
D) a person with one normal and one shortened (deleted) X
E) Down syndrome, 46, XX
23. Duchenne muscular dystrophy is a serious condition caused by a recessive allele
of a gene on the human X chromosome. The patients have muscles that weaken
over time because they have absent or decreased dystrophin, a muscle protein.
They rarely live past their 20s. How likely is it for a woman to have this
condition?
A) Women can never have this condition.
B) One-half of the daughters of an affected man would have this condition.
C) One-fourth of the daughters of an affected father and a carrier mother could
have this condition.
D) Very rarely: it is rare that an affected male would mate with a carrier female.
E) Only if a woman is XXX could she have this condition.
24. Which of the following statements is true of linkage?
A) The closer two genes are on a chromosome, the lower the probability that a
crossover will occur between them.
B) The observed frequency of recombination of two genes that are far apart from
each other has a maximum value of 100%.
C) All of the traits that Mendel studied–seed color, pod shape, flower color, and
others–are due to genes linked on the same chromosome.
D) Linked genes are found on different chromosomes.
E) Crossing over occurs during prophase II of meiosis.
25. What does a frequency of recombination of 50% indicate?
A) The two genes are likely to be located on different chromosomes.
B) All of the offspring have combinations of traits that match one of the two
parents.
C) The genes are located on sex chromosomes.
D) Abnormal meiosis has occurred.
E) Independent assortment is hindered.
26. Three genes (A, B, and C) at three loci are being mapped in a particular species.
Each gene has two alleles, one of which results in a phenotype that is markedly
different from the wild type. The unusual allele of gene A is inherited with the
unusual allele of gene B or C about 50% of the time. However, the unusual alleles
of genes B and C are recombined 14.4% of the time. Which of the following
describes what is happening?
A) The three genes are showing independent assortment.
B) The three genes are linked.
C) Gene A is linked but genes B and C are not.
D) Gene A is assorting independently of genes B and C, which are linked.
E) Gene A is located 14.4 map units from genes B and C.
27. If cell X enters meiosis, and nondisjunction of one chromosome occurs in one of
its daughter cells during meiosis I, what will be the result at the completion of
meiosis?
A) All the gametes descended from cell X will be diploid.
B) Half of the gametes descended from cell X will be n + 1, and half will be n - 1.
C) One-fourth of the gametes descended from cell X will be n + 1, 1/4 will be n 1, and 1/2 will be n.
D) There will be three extra gametes.
E) Two of the four gametes descended from cell X will be haploid, and two will
be diploid.
28. One possible chromosomal mutation is the replication of one particular segment
of a chromosome. What is this alteration called?
A) deletion
B) transversion
C) inversion
D) translocation
E) duplication
29.
Figure 12.1 below shows a map of four genes on a chromosome
Between which two genes would you expect the lowest frequency of recombination?
A) A and W
B) W and E
C) E and G
D) A and E
E) A and G
Fig. 12.2
30. In a series of mapping experiments, the recombination frequencies for four
different linked genes of Drosophila were determined as shown in Figure 12.2.
What is the order of these genes on a chromosome map?
A) rb-cn-vg-b
B) vg-b-rb-cn
C) cn-rb-b-vg
D) b-rb-cn-vg
E) vg-cn-b-rb
Use the following information to answer the questions below.
A plantlike organism on the planet Pandora can have three recessive genetic traits: bluish
leaves, due to an allele (a) of gene A; a feathered stem, due to an allele (b) of gene B; and
hollow roots due to an allele (c) of gene C. The three genes are linked and recombine as
follows:
A geneticist did a testcross with an organism that had been found to be heterozygous for
the three recessive traits and she was able to identify progeny of the following phenotypic
distribution (+ = wild type):
Fig. 12.3
31. Which of the following are the phenotypes of the parents in this cross?
A) 2 and 5
B) 1 and 6
C) 4 and 8
D) 3 and 7
E) 1 and 2
32. In which progeny phenotypes has there been recombination between genes A and
B?
A) 1, 2, 5, and 6
B) 1, 3, 6, and 7
C) 2, 4, 5, and 8
D) 2, 3, 5, and 7
E) in all 8 of them
33. If recombination frequency is equal to distance in map units, what is the
approximate distance between genes A and B?
A) 1.5 map units
B) 3 map units
C) 6 map units
D) 15 map units
E) 30 map units
34. Use the pedigree above. Which of the following could NOT be the pattern of
inheritance for this trait? There may be two answers.
a. autosomal dominant
b. autosomal recessive
c. X-linked dominant
d. X-linked recessive
35. Use the pedigree above. Which of the following is the pattern of inheritance
for this trait? There may be two answers.
a. autosomal dominant
b. autosomal recessive
c. X-linked dominant
d. X-linked recessive
36. Skin color in a certain species of fish is inherited via a single gene with four
different alleles.
One fish of this type has alleles 1 and 3 (S1S3) and its mate has alleles 2 and 4
(S2S4). If each allele confers a unit of color darkness such that S1 has one unit, S2
has two units, and so on, then what proportion of their offspring would be
expected to have five units of color?
A) 1/4
B) 1/5
C) 1/8
D) 1/2
E) 0
37. What is the reason that closely linked genes are typically inherited together?
A) The likelihood of a crossover event between these two genes is low.
B) The number of genes in a cell is greater than the number of chromosomes.
C) Chromosomes are unbreakable.
D) Alleles are paired together during meiosis.
E) Genes align that way during metaphase I of meiosis.
38. Remember to practice Chi-Square Problems!
ANSWER KEY
1. C
2. C
3. A
4. D
5. E
6. C
7. D
8. D
9. E
10. A
11. E
12. A
13. C
14. B
15. C
16. C
17. B
18. D
19. BO
20. D
21. E
22. B
23. D
24. A
25. A
26. D
27. B
28. E
29. B
30. D
31. C
32. A
33. B
34. B+D
35. B
36. D
37. A