Transcript on the X chromosome of a male

CAMPBELL BIOLOGY IN FOCUS
Urry • Cain • Wasserman • Minorsky • Jackson • Reece
12
The Chromosomal
Basis of Inheritance
Questions prepared by
Brad Stith, University of Colorado Denver
Janet Lanza, University of Arkansas at Little Rock
Louise Paquin, McDaniel College
© 2014 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 the Mendelian concept of
the gene and the movement/pairing of chromosomes.
C. It allowed scientists to see the nucleotide sequence of DNA.
D. It led to the discovery of mitochondria.
E. It showed genes functioning to direct the formation of
enzymes.
© 2014 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 the Mendelian concept of
the gene and the movement/pairing of chromosomes.
C. It allowed scientists to see the nucleotide sequence of DNA.
D. It led to the discovery of mitochondria.
E. It showed genes functioning to direct the formation of
enzymes.
© 2014 Pearson Education, Inc.
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 or 46w
C. w or w on X
D. 2  3
© 2014 Pearson Education, Inc.
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 or 46w
C. w or w on X
D. 2  3
© 2014 Pearson Education, Inc.
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?
© 2014 Pearson Education, Inc.
Imagine that Morgan had used a grasshopper
(2n  24, and sex is determined as follows: male has
X, and female has XX) to study sex linkage. 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
© 2014 Pearson Education, Inc.
Imagine that Morgan had used a grasshopper
(2n  24, and sex is determined as follows: male has
X, and female has XX) to study sex linkage. 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
© 2014 Pearson Education, Inc.
Think about bees and ants where there are no X and Y sex
chromosomes. Males are haploid, whereas fertilization results in
females, as diploid cells become females. 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
© 2014 Pearson Education, Inc.
Think about bees and ants where there are no X and Y sex
chromosomes. Males are haploid, whereas fertilization results in
females, as diploid cells become females. 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
© 2014 Pearson Education, Inc.
Determination of sex in Drosophila is similar to that in humans. In
some species of Drosophila, 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.
© 2014 Pearson Education, Inc.
Determination of sex in Drosophila is similar to that in humans. In
some species of Drosophila, 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.
© 2014 Pearson Education, Inc.
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.
© 2014 Pearson Education, Inc.
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.
© 2014 Pearson Education, Inc.
Imagine two species of cats 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.
© 2014 Pearson Education, Inc.
Imagine two species of cats 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.
© 2014 Pearson Education, Inc.
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.
© 2014 Pearson Education, Inc.
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.
© 2014 Pearson Education, Inc.
Triploid species are usually sterile (unable to reproduce),
whereas tetraploids are often fertile. Which of the following is
likely a good explanation of these facts? Hint: synapsis.
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.
© 2014 Pearson Education, Inc.
Triploid species are usually sterile (unable to reproduce),
whereas tetraploids are often fertile. Which of the following is
likely a good explanation of these facts? Hint: synapsis.
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.
© 2014 Pearson Education, Inc.
Chromosomal rearrangements can occur after chromosomes
break. Which of the following statements is 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 one
that is homozygous for a duplication of that same
gene because loss of a function can be lethal.
© 2014 Pearson Education, Inc.
Chromosomal rearrangements can occur after chromosomes
break. Which of the following statements is 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 one
that is homozygous for a duplication of that same
gene because loss of a function can be lethal.
© 2014 Pearson Education, Inc.
Imagine that you could create medical policy for a
country. In this country it is known that the frequency of
Down syndrome increases with increasing age of the
mother and that the frequency of schizophrenia and
autism increases with the age of the father. In both, 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
children with Down syndrome. What kind of policy
regarding fetal testing would you implement?
© 2014 Pearson Education, Inc.