Transcript 15_Active_Lecture_Questions

Active Lecture Questions for
BIOLOGY, Eighth Edition
Neil Campbell & Jane Reece
Chapter 15
The Chromosomal Basis of
Inheritance
Questions prepared by
Janet Lanza,
University of Arkansas at Little Rock
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings.
Morgan’s Experimental Evidence
Imagine that Morgan had chosen a different
organism for his genetics experiments. Which of
the following species would have made a better
choice than fruit flies?
a) a plant that could be self-pollinated
b) a species with many small chromosomes
c) a species with more genetic diversity
d) a species with a one-week generation time
e) all of the above
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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 orange because the functional allele O
converts eumelanin into phaeomelanin.
b)
The phenotype of o-Y males is black/brown because the non-functional
allele o does not convert eumelanin into phaeomelanin.
c)
The phenotype of OO and Oo males is orange because the functional allele
O converts eumelanin into phaeomelanin.
d)
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 non-functional allele o
does not convert eumelanin into phaeomelanin.
e)
The phenotype of O-Y males is orange because the non-functional 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings.
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 females is orange because the functional allele O
converts eumelanin into phaeomelanin.
b)
The phenotype of o-Y females is black/brown because the non-functional allele
o does not convert eumelanin into phaeomelanin.
c)
The phenotype of OO and Oo females is orange because the functional allele O
converts eumelanin into phaeomelanin.
d)
The phenotype of Oo females 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 non-functional allele o does not
convert eumelanin into phaeomelanin.
e)
The phenotype of O-Y females is orange because the non-functional 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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings.
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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings.
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. The graph on the next slide shows the
incidence of Down syndrome as a function of maternal age. Which of
the following policies would you implement?
a)
No testing of pregnant women should be conducted and all the health care
money should be used for training of Down syndrome children.
b)
The health care system should provide testing only for women over 30.
c)
The health care system should provide testing only for women over 40.
d)
The health care system should require termination of all Down syndrome
fetuses.
e)
The health care system should provide training for the 30% most seriously
affected children only.
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Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings.
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.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings.