A woman is found to have forty-seven chromosomes, including three X
chromosomes. Which of the following describes her expected phenotype?
Answers:
a female with masculine characteristics such as facial
hair an apparent male who is sterile healthy female
of slightly above-average height a sterile female
3
A man who carries an allele of an X-linked gene will pass it on to _____.
Answers:
all of his daughters half of his daughters
all of his sons all of his children
1
In rabbits, the homozygous CC is normal, Cc results
in deformed legs, and cc results in very short legs. The
genotype BB produces black fur, Bb brown fur, and
bb white fur. If a cross is made between brown rabbits with
deformed legs and white rabbits with deformed legs, what percentage of
the offspring would be expected to have deformed legs and white fur?
Answers:
25% 33% 100% 50%
1
Feather color in budgies is determined by two different genes,
Y and B, one for pigment on the outside and one for
the inside of the feather. YYBB, YyBB, or
YYBb is green; yyBB or yyBb is blue;
YYbb or Yybb is yellow; and yybb is white.
A blue budgie is crossed with a white budgie. Which of the following
results is NOT possible?
Answers:
green offspring only yellow offspring only
blue offspring only green and yellow offspring
4
What is the reason that closely linked genes are typically inherited together?
Answers:
They are located close together on the same chromosome.
The number of genes in a cell is greater than the number of
chromosomes. Alleles are paired together during meiosis.
Genes align that way during metaphase I of meiosis.
1
Of the following human aneuploidies, which is the one that generally
has the most severe impact on the health of the individual?
Answers:
47, trisomy 21 47, XXY 47, XXX 45,
X
1
In a Drosophila experiment, a cross was made between
homozygous wild-type females and yellow-bodied males. All of the
resulting F1s were phenotypically wild type. However, adult
flies of the F2 generation (resulting from matings of the
F1s) had the characteristics shown in the figure above.
Consider the following questions:(a) Is the mutant allele for
yellow body recessive or dominant?(b) Is the yellow locus
autosomal (not X-linked) or X-linked?
Answers:
(a) recessive; (b) X-linked (a) recessive; (b) not
X-linked (a) dominant; (b) X-linked (a) dominant;
(b) not X-linked
1
Use the figure and the following description to answer the
question(s) below.
In a particular plant, leaf color is controlled by gene locus
D. Plants with at least one allele D have dark green
leaves, and plants with the homozygous recessive dd genotype
have light green leaves. A true-breeding, dark-leaved plant is crossed
with a light-leaved one, and the F1 offspring is allowed to
self-pollinate. The predicted outcome of the F2 is
diagrammed in the Punnett square shown in the figure, where 1, 2, 3,
and 4 represent the genotypes corresponding to each box within the square.
Which of the boxes marked 1-4 correspond to plants with a
heterozygous genotype?
Answers:
1 1, 2, and 3 2 and 3 2, 3, and
4
3
What was the most significant conclusion that Gregor Mendel drew from
his experiments with pea plants?
Answers:
There is considerable genetic variation in garden peas.
Traits are inherited in discrete units and are not the results
of "blending." Recessive genes occur more
frequently in the F1 generation than do dominant
ones. Genes are composed of DNA.
2
Which of the following is an example of polygenic inheritance?
Answers:
pink flowers in snapdragons the ABO blood group in
humans white and purple flower color in peas skin
pigmentation in humans
4
Males are more often affected by sex-linked traits than females
because _____.
Answers:
male hormones such as testosterone often alter the effects of
mutations on the X chromosome female hormones such as
estrogen often compensate for the effects of mutations on the X
chromosome X chromosomes in males generally have more
mutations than X chromosomes in females males are
hemizygous for the X chromosome
4
A woman who has blood type A positive has a daughter who is type O
positive and a son who is type B negative. Rh positive is a trait that
shows simple dominance over Rh negative. Which of the following is a
possible phenotype for the father?
Answers:
A negative O negative B positive AB
negative
3
Which of the following provides an example of epistasis?
Answers:
Recessive genotypes for each of two genes (aabb)
results in an albino corn snake. In rabbits and many other
mammals, one genotype (ee) prevents any fur color from
developing. In Drosophila (fruit flies), white eyes
can be due to an X-linked gene or to a combination of other
genes. In cacti, there are several genes for the type of
spines.
2
Mendel's observation of the segregation of alleles in gamete
formation has its basis in which of the following phases of cell division?
Answers:
prophase I of meiosis anaphase II of meiosis
metaphase II of meiosis anaphase I of meiosis
4
A recessive allele on the X chromosome is responsible for red-green
color blindness in humans. A woman with normal vision whose father is
color blind marries a color-blind male. What is the probability that
this couple's first son will be color blind?
Answers:
1/4 1/2 2/3 3/4
2
A black guinea pig crossed with an albino guinea pig produced twelve
black offspring. When the albino was crossed with a second black
animal, six blacks and six albinos were obtained. What is the best
explanation for this genetic situation?
Answers:
Albino is recessive; black is dominant. Albino is
dominant; black is incompletely dominant. Albino and black
are codominant. Albino is recessive; black is
codominant.
1
Which of the following is the meaning of the chromosome theory of
inheritance as expressed in the early twentieth century?
Answers:
Individuals inherit particular chromosomes attached to
genes. Mendelian genes are at specific loci on the chromosome
and, in turn, segregate during meiosis. No more than a
single pair of chromosomes can be found in a healthy normal
cell. Natural selection acts on certain chromosome arrays
rather than on genes.
2
Radish flowers may be red, purple, or white. A cross between a
red-flowered plant and a white-flowered plant yields all-purple
offspring. The part of the radish we eat may be oval or long, with
long being the dominant trait. If true-breeding red long radishes are
crossed with true-breeding white oval radishes, the F1 will
be expected to be which of the following?
Answers:
red and long white and long purple and
long purple and oval
3
The following questions refer to the pedigree chart in the figure
below for a family, some of whose members exhibit the dominant trait,
W. Affected individuals are indicated by a dark square or circle.
What is the probability that individual III-1 is Ww?
Answers:
3/4 1/4 2/4 1
4
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?
Answers:
1/16 3/8 1/2 9/16
3