Transcript Chapter 2

CLICKER QUESTIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Chapter 15
The Chromosomal Basis of
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Inheritance
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Questions prepared by
Janet Lanza
University of Arkansas at Little Rock
Louise Paquin
McDaniel College
© 2011 Pearson Education, Inc.
Why did the improvement of microscopy
techniques in the late 1800s set the stage for
the emergence of modern genetics?
a) It revealed new and unanticipated features of Mendel's
pea plant varieties.
b) It allowed the study of meiosis and mitosis, revealing
parallels between behaviors of genes and chromosomes.
c) It allowed scientists to see the DNA present within
chromosomes.
d) It led to the discovery of mitochondria.
e) It showed genes functioning to direct the formation of
enzymes.
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Morgan and his colleagues worked out a set of
symbols to represent fly genotypes. Which of
the following are representative?
a) AaBb × AaBb
b) 46, XY or 46, XX
c) vg+vgse+se × vgvgsese
d) +2 × +3
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Morgan’s Experimental Evidence
Imagine that Morgan had chosen a different
organism for his genetics experiments. What kind
of species would have made a better choice than
fruit flies?
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Morgan’s Experimental Evidence
Imagine that Morgan had used a grasshopper
(2n = 24 and an XX, XO sex determination
system). Predict where the first mutant would
have been discovered.
a) on the O chromosome of a male
b) on the X chromosome of a male
c) on the X chromosome of a female
d) on the Y chromosome of a male
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The Chromosomal Basis of Sex
Think about bees and ants, groups in which males are haploid.
Which of the following are accurate statements about bee and
ant males when they are compared to species in which males
are XY and diploid for the autosomes?
a) Bee males have half the DNA of bee females, whereas
human males have nearly the same amount of DNA that
human females have.
b) Considered across the genome, harmful (deleterious)
recessives will negatively affect bee males more than
Drosophila males.
c) Human and Drosophila males have sons, but bee males do
not.
d) Inheritance in bees is like inheritance of sex-linked
characteristics in humans.
e) none of the above
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The Chromosomal Basis of Sex
In some Drosophila species there are genes on the Y
chromosome that do not occur on the X chromosome.
Imagine that a mutation of one gene on the Y chromosome
reduces the size by half of individuals with the mutation.
Which of the following statements is accurate with regard to
this situation?
a) This mutation occurs in all offspring of a male with the mutation.
b) This mutation occurs in all male but no female offspring of a male
with the mutation.
c) This mutation occurs in all offspring of a female with the mutation.
d) This mutation occurs in all male but no female offspring of a female
with the mutation.
e) This mutation occurs in all offspring of both males and females with
the mutation.
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The Chromosomal Basis of Sex
Imagine that a deleterious recessive allele occurs on
the W chromosome of a chicken (2n = 78). Where
would it be most likely to appear first in a genetics
experiment?
a) in a male because there is no possibility of the presence
of a normal, dominant allele
b) in a male because it is haploid
c) in a female because there is no possibility of the
presence of a normal, dominant allele
d) in a female because all alleles on the W chromosomes
are dominant to those on the Z chromosome
e) none of the above
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Inheritance of Sex-Linked Genes
In cats, a sex-linked gene affects coat color. The O allele produces
an enzyme that converts eumelanin, a black or brown pigment, into
phaeomelanin, an orange pigment. The o allele is recessive to O
and produces a defective enzyme, one that does not convert
eumelanin into phaeomelanin. Which of the following statements
is/are accurate?
a)
The phenotype of o-Y males is black/brown because the nonfunctional allele
o does not convert eumelanin into phaeomelanin.
b)
The phenotype of OO and Oo males is orange because the functional allele
O converts eumelanin into phaeomelanin.
c)
The phenotype of Oo males is mixed orange and black/brown because the
functional allele O converts eumelanin into phaeomelanin in some cell
groups (orange) and because in other cell groups the nonfunctional allele o
does not convert eumelanin into phaeomelanin.
d)
The phenotype of O-Y males is orange because the nonfunctional allele O
does not convert eumelanin into phaeomelanin, while the phenotype of o-Y
males is black/brown because the functional allele o converts eumelanin
into phaeomelanin.
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X Inactivation in Female Mammals
Imagine two species of mammals that differ in the timing of Barr
body formation during development. Both species have genes
that determine coat color, O for the dominant orange fur and o
for the recessive black/brown fur, on the X chromosome. In
species A, the Barr body forms during week 1 of a 6-month
pregnancy whereas in species B, the Barr body forms during
week 3 of a 5-month pregnancy. What would you predict about
the coloration of heterozygous females (Oo) in the two species?
a) Both species will have similar sized patches of orange and
black/brown fur.
b) Species A will have smaller patches of orange or black/brown fur
than will species B.
c) The females of both species will show the dominant fur color,
orange.
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Mapping the Distance Between Genes
Imagine a species with three loci thought to be on the same
chromosome. The recombination rate between locus A and locus
B is 35% and the recombination rate between locus B and locus
C is 33%. Predict the recombination rate between A and C.
a) The recombination rate between locus A and locus C is either 2% or
68%.
b) The recombination rate between locus A and locus C is probably
2%.
c) The recombination rate between locus A and locus C is either 2% or
50%.
d) The recombination rate between locus A and locus C is either 2% or
39%.
e) The recombination rate between locus A and locus C cannot be
predicted.
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Triploid species are usually sterile (unable to
reproduce), whereas tetraploids are often
fertile. Which of the following are likely good
explanations of these facts?
a) In mitosis, some chromosomes in triploids have no partner at
synapsis, but chromosomes in tetraploids do have partners.
b) In meiosis, some chromosomes in triploids have no partner at
synapsis, but chromosomes in tetraploids do have partners.
c) In mitosis, some chromosomes in tetraploids have no partner
at synapsis, but chromosomes in triploids do have partners.
d) In meiosis, some chromosomes in tetraploids have no partner
at synapsis, but chromosomes in triploids do have partners.
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Chromosomal rearrangements can occur after
chromosomes break. Which of the following
statements are most accurate with respect to
alterations in chromosome structure?
a) Chromosomal rearrangements are more likely to occur in
mammals than in other vertebrates.
b) Translocations and inversions are not deleterious because no
genes are lost in the organism.
c) Chromosomal rearrangements are more likely to occur during
mitosis than during meiosis.
d) An individual that is homozygous for a deletion of a certain
gene is likely to be more damaged than is one that is
homozygous for a duplication of that same gene because loss
of a function can be lethal.
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Imagine that you could create medical policy for a
country. In this country it is known that the
frequency of Down syndrome babies increases
with increasing age of the mother and that the
severity of characteristics varies enormously and
unpredictably among affected individuals.
Furthermore, financial resources are severely
limited, both for testing of pregnant women and for
supplemental training of Down syndrome children.
What kind of policy regarding fetal testing would
you implement?
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The lawyer for a defendant in a paternity suit
asked for DNA testing of a baby girl. Which of the
following set of results would demonstrate that
the purported father was not actually the genetic
father of the child?
a) The mitochondrial DNA of the child and “father” did not match.
b) DNA sequencing of chromosome 5 of the child and “father”
did not match.
c) The mitochondrial DNA of the child and mother did not match.
d) DNA sequencing of chromosome 5 of the child and mother did
not match.
e) The mitochondrial DNA of the child and “father” matched but
the mitochondrial DNA of the child and mother did not.
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