CHAPTER 13—GENES, CHROMOSOMES, AND HUMAN GENETICS
MULTIPLE CHOICE
1. Progeria is a genetic condition that causes
a.
pattern baldness as early as age twenty.
b.
socially inappropriate vocal outbursts and muscular twitches.
c.
a high incidence of cancer with any exposure to sunlight.
d.
muscular and mental deterioration shortly after puberty.
e.
premature aging which typically leads to death in the early teens.
2. Linked genes are
a.
genes whose effects combine to affect a single characteristic.
b.
different alleles of the same gene.
c.
genes that affect two different traits and that lead to a 9:3:3:1 phenotype ratio in a dihybrid
cross.
d.
genes that do not sort independently due to their being physically near each other on the
same chromosome.
e.
genes on two different chromosomes
3. Exceptions to the principle of independent assortment were discovered and explained by ____ as
resulting from genes being physically associated with each other on the same chromosome.
a.
Watson
b.
Sturtevant
c.
Morgan
d.
Mendel
e.
Crick
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4. Suppose that in studies of genes on the same chromosome you find the following recombination
frequencies:
In this case it would be proper to say that a, c, and b are
a.
linked genes.
b.
different alleles of the same gene.
c.
alternative alleles that are not physically possible since the numbers do not add up.
d.
linked genes that are not physically possible since the numbers do not add up.
e.
three of the possible alleles for determining a particular trait.
5. Suppose that in studies of genes on the same chromosome you find the following recombination
frequencies:
Why do the distances between a-c and c-b not add up to the distance between a-b?
a.
a and b are not linked
b.
the distances were calculated incorrectly
c.
b is in between the a and c genes
d.
double crossovers between a-b decrease recombinants
e.
all three genes encode the same trait
6. Genetic studies of an animal show that eye color is controlled by an autosomal gene with the dominant
allele (R) for red eye color and the recessive allele (r) for yellow eye color. A second autosomal gene
has the dominant allele (T) leading to paws with thumbs while the recessive allele (t) codes for paws
without thumbs. The genetic cross RRTT rrtt creates offspring with genotype RrTt. One of those
dihybrids is mated in a testcross (RrTt rrtt). Based on the principle of independent assortment the
testcross should produce offspring with the phenotype ratio
a.
3 red-eyed with thumbs: 1 yellow-eyed without thumbs.
b.
1 red-eyed with thumbs: 1 yellow-eyed with thumbs: 1 red-eyed without thumbs: 1
yellow-eyed without thumbs.
c.
1 red-eyed with thumbs: 1 yellow-eyed without thumbs.
d.
9 red-eyed with thumbs: 3 yellow-eyed with thumbs: 3 red-eyed without thumbs: 1
yellow-eyed without thumbs.
e.
3 yellow-eyed with thumbs: 1 red-eyed without thumbs.
7. Genetic studies of an animal show that eye color is controlled by an autosomal gene with the dominant
allele (R) for red eye color and the recessive allele (r) for yellow eye color. A second autosomal gene
has the dominant allele (T) leading to paws with thumbs while the recessive allele (t) codes for paws
without thumbs. The genetic cross RRTT rrtt creates offspring with genotype RrTt. One of those
dihybrids is mated in a testcross (RrTt rrtt). If the two genes are completely linked (no
recombination occurs between them), then the testcross should produce offspring with the phenotype
ratio
a.
3 red-eyed with thumbs: 1 yellow-eyed without thumbs.
b.
1 red-eyed with thumbs: 1 yellow-eyed with thumbs: 1 red-eyed without thumbs: 1
yellow-eyed without thumbs.
c.
1 red-eyed with thumbs: 1 yellow-eyed without thumbs.
d.
9 red-eyed with thumbs: 3 yellow-eyed with thumbs: 3 red-eyed without thumbs: 1
yellow-eyed without thumbs.
e.
1 yellow-eyed with thumbs: 1 red-eyed without thumbs.
8. A butterfly of genotype CCdd is crossed to ccDD and the F1 testcrossed to ccdd. If the genes are
linked and 30cM apart, what fraction of the F2 offspring should be ccdd?
a.
15%
b.
30%
c.
50%
d.
70%
e.
85%
9. If two genes are linked on the same chromosome, then
a.
they tend to segregate away from one another during meiosis
b.
the closer they are to each other the more crossing over occurs between them
c.
the closer they are to each other the less crossing over occurs between them
d.
they tend to segregate away from one another during mitosis
e.
they control the same trait
10. The map distances for four linked genes are as follows: A is 22mu from B, B is 7mu from C, C is 9mu
from D, B is 2mu from D, A is 20mu from D, and A is 29mu from C. Based on these data, what is the
order of these four genes on the chromosome?
a.
ABCD
b.
ADBC
c.
ABDC
d.
BADC
e.
CADB
11. When two genes on the same chromosome are located 10 map units from each other, ____ of the
offspring from a testcross for genetic linkage should have a recombinant phenotype.
a.
over 75%
b.
about 50%
c.
about 25%
d.
about 10%
e.
about 5%
12. When two genes are located on different chromosomes, ____ of the offspring from a testcross for
genetic linkage should have a recombinant phenotype.
a.
over 75%
b.
about 50%
c.
about 25%
d.
about 10%
e.
about 5%
13. Recombination frequency for two genes is a function of
a.
the distance between the two genes on a single chromosome.
b.
the overall size of the chromosome where the genes are located.
c.
the distance between the two chromosomes that each have one of the two genes.
d.
the relative sizes of the two chromosomes that each have one of the two genes.
e.
the sex of the parent that supplies each gene.
14. In Drosophila melanogaster the allele for red eyes is dominant over the allele for purple eyes, and the
allele for a gray body is dominant over the allele for a black body. A testcross was done to check for
genetic linkage between the genes for these traits, with the following results for the offspring:
478 flies with red eyes and a black body
27 flies with red eyes and a gray body
462 flies with purple eyes and a gray body
33 flies with purple eyes and a black body
Which of the choices below best represents the map distance between the genes for these two traits?
a.
50.0 map units
b.
30.0 map units
c.
47.0 map units
d.
27.0 map units
e.
6.0 map units
15. In Drosophila melanogaster the allele for long wings is dominant over the allele for vestigial wings,
and the allele for a gray body is dominant over the allele for a black body. A testcross was done to
check for genetic linkage between the genes for these traits, with the following results for the
offspring:
410 flies with long wings and a black body
105 flies with long wings and a gray body
390 flies with vestigial wings and a gray body
95 flies with vestigial wings and a black body
Which of the choices below best represents the map distance between the genes for these two traits?
a.
20.0 map units
b.
40.0 map units
c.
10.0 map units
d.
100.0 map units
e.
9.5 map units
16. The concept of mapping genes on chromosomes was developed by ____ when he was an
undergraduate student.
a.
Watson
b.
Sturtevant
c.
Morgan
d.
Mendel
e.
Crick
17. You are given a genetic mapping project as an undergraduate research assistant. You are told that
genes a and b are 7.4 map units from each other and that genes b and c are 5.7 map units from each
other. You do a cross to determine the map distance between a and c. Which of the following results
would indicate that c lies between a and b?
a.
11.1 map units
b.
15.0 map units
c.
2.0 map units
d.
14.8 map units
e.
13.1 map units
18. Genetic map units represent
a.
absolute physical distances between genes.
b.
locations of different alleles of a gene.
c.
the chromosome on which a given gene is located.
d.
the actual DNA sequence of a gene.
e.
relative positions of genes with respect to each other.
19. Which process generally is the cause for production of recombinant offspring for two genes on the
same chromosome?
a.
movement of transposable elements
b.
pairing of nonhomologous chromosomes
c.
gene duplication
d.
exon shuffling
e.
crossing over between homologous chromosomes
20. The discovery of sex-linked genes and production of the first chromosome map came from studies of
a.
pea plants.
b.
corn.
c.
humans.
d.
fruit flies.
e.
mice.
21. For an individual Drosophila melanogaster fly the time from when it is laid as an egg to when it is an
adult capable of breeding is about ____.
a.
3 months
b.
2 days
c.
6 weeks
d.
10 days
e.
1 month
22. The genome of Drosophila melanogaster contains about ____ genes.
a.
1,000
b.
14,000
c.
165 million
d.
3 billion
e.
20,000
23. Sex-linked genes are genes that are
a.
expressed differently based on the sex of an individual.
b.
linked to the sex determining gene.
c.
located on sex chromosomes.
d.
determinants of the sex of an individual.
e.
found exclusively in one sex or the other.
24. In humans, sex determination generally depends upon
a.
whether or not the X chromosome is present.
b.
the number of X chromosomes present.
c.
environment in the womb.
d.
whether or not the Y chromosome is present.
e.
how many autosomes are present
25. An autosome is
a.
a chromosome that is part of a pair that is the same in both males and females.
b.
a structure for transport of genetic material to the cytoplasm.
c.
a chromosome with a group of genes involved in autoimmune disorders.
d.
a region of the DNA that is self-replicating.
e.
a cellular body involved in autoimmune disorders.
26. In birds and butterflies ____ for sex chromosome inheritance.
a.
males are XY and females are XX
b.
males are ZZ and females are ZW
c.
males are ZY and females are XW
d.
males are XX and females are XY
e.
males are ZW and females are ZZ
27. In humans, normally if ____ then the SRY gene switches development toward ____ at an early point in
embryonic development.
a.
a Y chromosome is present; maleness
b.
an X chromosome is present; femaleness
c.
two X chromosomes are present; femaleness
d.
no X chromosome is present; maleness
e.
a Y chromosome is present; femaleness
28. In Drosophila melanogaster there is a sex-linked gene for eye color that is found only on the X
chromosome. The allele for red eye color (Xw+) is dominant over the allele for white eye color (Xw).
You examine a vial of 100 flies that are all offspring from a single genetic cross. You see only red-
eyed females present, but you see both red-eyed and white-eyed males present. The genotypes of the
parents were
a.
Xw+Xw+; Xw+Y.
b.
XwXw; Xw+Y.
c.
Xw+Xw; XwY.
d.
Xw+Xw; Xw+Y.
e.
XwXw; XwY.
29. In Drosophila melanogaster there is a sex-linked gene for eye color that is found only on the X
chromosome. The allele for red eye color (Xw+) is dominant over the allele for white eye color (Xw).
You examine a vial of 100 flies that are all offspring from a single genetic cross. You find both red-
eyed females and white-eyed females as well as both red-eyed males and white-eyed males. The
genotypes of the parents were
a.
Xw+Xw+; XwY.
b.
Xw+Xw; XwY.
c.
XwXw; Xw+Y.
d.
Xw+Xw; Xw+Y.
e.
XwXw; XwY.
30. In Drosophila melanogaster there is a sex-linked gene for eye color that is found only on the X
chromosome. The allele for red eye color (Xw+) is dominant over the allele for white eye color (Xw).
You examine a vial of 100 flies that are all offspring from a single genetic cross. You see only red–
eyed females and white-eyed males present. The genotypes of the parents were
a.
Xw+Xw+; XwY.
b.
Xw+Xw; XwY.
c.
XwXw; Xw+Y.
d.
Xw+Xw; Xw+Y.
e.
XwXw; XwY.
31. In Drosophila melanogaster there is a sex-linked gene for eye color that is found only on the X
chromosome. The allele for red eye color (Xw+) is dominant over the allele for white eye color (Xw).
You examine a vial of 100 flies that are all offspring from a single genetic cross. You find only red-
eyed females and red-eyed males present. Flies from the vial were allowed to interbreed, and in the
next generation you find only red-eyed females, but you find both red-eyed and white-eyed males. The
genotypes of the original parents were
a.
Xw+Xw+; XwY.
b.
Xw+Xw; XwY.
c.
XwXw; Xw+Y.
d.
Xw+Xw; Xw+Y.
e.
XwXw; XwY.
32. An individual who is a carrier of a genetically inherited disease
a.
has the disease, and any of their offspring will have the disease.
b.
does not have the disease but must have a parent with the disease.
c.
does not have the disease but may have offspring with the disease.
d.
has the disease and must have a parent with the disease.
e.
does not have the disease but must have a parent with the disease and may have offspring
with the disease.
33. A woman with normal blood clotting mates with a man who has hemophilia. Their first child is a boy
who has hemophilia. Tests show that the father and son both have the same form of hemophilia, that it
is X-linked, and that the boy has normal genetic inheritance. You can predict that if the couple
produces more children together, then the odds are that
a.
all of the children will have hemophilia.
b.
half of the boys and none of the girls will have hemophilia.
c.
none of the rest of children should have hemophilia.
d.
all of the boys and half of the girls will have hemophilia.
e.
half of the boys and half of the girls will have hemophilia.
34. A woman with normal blood clotting mates with a man who also has normal blood clotting. Their first
child is a boy who has hemophilia. Tests show that the child’s hemophilia is X-linked and that he has
normal genetic inheritance. You can predict that if the couple produces more children together, then
the odds are that
a.
all of the children will have hemophilia.
b.
half of the boys and none of the girls will have hemophilia.
c.
none of the rest of children should have hemophilia.
d.
all of the boys and half of the girls will have hemophilia.
e.
half of the boys and half of the girls will have hemophilia.
35. In placental mammals such as humans the dosage compensation mechanism to essentially equalize
expression of sex-linked genes in males and females is
a.
doubling the gene expression for most genes on the X chromosome in males.
b.
doubling the number of X chromosomes in males early in embryonic development in all
cells except for precursors of sex cells.
c.
having all major genes on the X chromosome also present on the Y chromosome.
d.
halving the gene expression for most genes on each X chromosome in females.
e.
inactivation of one of the two X chromosomes in most body cells of females.
36. If you see a male calico cat, you can be fairly certain that his diploid cells have a sex chromosome
combination of ____.
a.
XYY
b.
XY
c.
XX
d.
XXY
e.
XO
37. The change in the chromosomes depicted between the top and the bottom in the figure above
represents a(n) ____.
a.
inversion
b.
duplication
c.
reciprocal translocation
d.
deletion
e.
Philadelphia chromosome
38. The change in the chromosome depicted between the top and the bottom in the figure above represents
a(n) ____.
a.
inversion
b.
duplication
c.
reciprocal translocation
d.
deletion
e.
Philadelphia chromosome
39. The change in the chromosome depicted between the top and the bottom in the figure above represents
a(n) ____.
a.
inversion
b.
duplication
c.
reciprocal translocation
d.
deletion
e.
Philadelphia chromosome
40. The change in the chromosome depicted between the top and the bottom in the figure above represents
a(n) ____.
a.
inversion
b.
duplication
c.
reciprocal translocation
d.
deletion
e.
Philadelphia chromosome
41. Which of the following are generally not lethal to the individual in which they occur?
a.
duplications and deletions
b.
inversions and translocations
c.
inversions and deletions
d.
translocations and duplications
e.
all four of these are lethal
42. In humans a deletion from chromosome 5 typically leads to severe mental retardation and a malformed
larynx; this disorder is known as ____.
a.
Turner syndrome
b.
Down syndrome
c.
cri-du-chat
d.
Triple-X syndrome
e.
Klinefelter syndrome
43. If a hypothetical human female of genotype XX had no Barr body in any of her cells
a.
she would be phenotypically male
b.
she would be considered triploid
c.
the genes on both X chromosomes would be expressed
d.
she would have Turner syndrome
e.
she would have a Y chromosome
44. The presences of different genes for several types of hemoglobin in mammals, but not in sharks and
many other vertebrates, is evidence of ____ of genetic material.
a.
an inversion
b.
duplication
c.
reciprocal translocation
d.
deletion
e.
both duplication and deletion
45. Nondisjunction refers to
a.
failure of homologous pairs to separate during meiosis.
b.
improper pairing of nonhomologous chromosomes during meiosis.
c.
failure of sister chromatids to pair during mitosis.
d.
failure of homologous pairs or sister chromatids to separate during meiosis.
e.
failure of homologous pairs to separate during mitosis.
46. Individuals with extra or missing copies of some of their chromosomes are called ____.
a.
polyploids
b.
haploids
c.
aneuploids
d.
euploids
e.
diploids
47. Individuals with three or more copies of each of their chromosomes are called ____.
a.
polyploids
b.
haploids
c.
aneuploids
d.
euploids
e.
diploids
48. Which is most likely to happen to a human polyploid?
a.
natural abortion
b.
death around the age of 1 year
c.
survival until the early teens
d.
survival until the mid-thirties
e.
death around the age of 1 month
49. Examinations of miscarried human embryos show that about 70% of such embryos are ____.
a.
polyploids
b.
haploids
c.
aneuploids
d.
euploids
e.
diploids
50. In cells of human individuals with three or more X chromosomes
a.
one X chromosome remains active and the rest are inactivated.
b.
all of the X chromosomes remain active.
c.
two X chromosomes remain active, and any more are inactivated.
d.
two X chromosomes remain active in females and one remains active in males; the rest are
inactivated.
e.
only one X chromosome is inactivated.