BIOL133 EXAM QUESTIONS AND
VERIFIED ANSWERS| 100% CORRECT
True or False. It is always the maternal X-chromosome that is inactivated during X-
inactivation.
False - At a few thousand cell stage of the embryo the inactivation of one X chromosome
occurs. The X-chromosome is chosen at random, though once chosen it remains inactivated
in all the descendants of that cell.
You are working as a cytologist (scientists who study cells and cell abnormalities) and you are
given some cells from a male patient. You note that these cells all have a single Barr body.
You do further analysis and see that all cells also have a Y chromosome. Which of the
following must be true of this male patient?
The patient is XXY.
The patient is phenotypically female.
The patient should produce sperm with the normal chromosome complement.
The patient will have hemophilia.
The patient is XXY
In cats, black fur color is caused by an X-linked allele; the other allele at this locus causes
orange color. The heterozygote is tortoiseshell. What kinds of offspring would you
expect from the cross of a black female and an orange male?
tortoiseshell females; black males
Which of the following is true of the SRY gene? Select all that apply.
,SRY is a gene region present on the Y chromosome that triggers male development.
SRY is an autosomal gene that is required for the expression of genes on the X chromosome.
SRY is an autosomal gene that is required for the expression of genes on the Y chromosome.
SRY is a gene present on the X chromosome that triggers female development.
An individual with an X and Y chromosome but a missing SRY gene will develop female
sex characteristics.
Correct:
SRY is a gene region present on the Y chromosome that triggers male development.
An individual with an X and Y chromosome but a missing SRY gene will develop female
sex characteristics.
Incorrect:
SRY is an autosomal gene that is required for the expression of genes on the X chromosome.
SRY is an autosomal gene that is required for the expression of genes on the Y chromosome.
SRY is a gene present on the X chromosome that triggers female development.
The gene responsible for X-inactivation is
XIST
You are working as a cytogeneticist (a scientist who looks for and evaluates chromosomal
and genetic abnormalities) and you have been asked to look at cell samples from a woman
who is experiencing infertility. You first stain the cells to look for Barr bodies and you find
that she has two Barr bodies in each cell. Which of the following is a possible conclusion
about her sex chromosomes?
She is genotype XXX.
, She has only a single X chromosome.
She is XXY with a non-functional Y chromosome.
She is genotype XX.
She is genotype XXX.
A person with Turner's Syndrome only has a single X sex chromosome. Which of the following
must be true of a person with Turner's syndrome? Select all that apply.
This person is most likely phenotypically female.
This person is most likely phenotypically male.
This person will have Barr bodies in their cells.
This person will not have Barr bodies in their cells.
This person will have 46 chromosomes in their body
cells. This person will have 45 chromosomes in their
body cells. Correct:
This person is most likely phenotypically female
This person will not have Barr bodies in their cells.
This person will have 45 chromosomes in their body cells.
Incorrect:
This person is most likely phenotypically male.
This person will have Barr bodies in their cells.
This person will have 46 chromosomes in their body cells.
Males are more often affected by sex-linked traits than females because
VERIFIED ANSWERS| 100% CORRECT
True or False. It is always the maternal X-chromosome that is inactivated during X-
inactivation.
False - At a few thousand cell stage of the embryo the inactivation of one X chromosome
occurs. The X-chromosome is chosen at random, though once chosen it remains inactivated
in all the descendants of that cell.
You are working as a cytologist (scientists who study cells and cell abnormalities) and you are
given some cells from a male patient. You note that these cells all have a single Barr body.
You do further analysis and see that all cells also have a Y chromosome. Which of the
following must be true of this male patient?
The patient is XXY.
The patient is phenotypically female.
The patient should produce sperm with the normal chromosome complement.
The patient will have hemophilia.
The patient is XXY
In cats, black fur color is caused by an X-linked allele; the other allele at this locus causes
orange color. The heterozygote is tortoiseshell. What kinds of offspring would you
expect from the cross of a black female and an orange male?
tortoiseshell females; black males
Which of the following is true of the SRY gene? Select all that apply.
,SRY is a gene region present on the Y chromosome that triggers male development.
SRY is an autosomal gene that is required for the expression of genes on the X chromosome.
SRY is an autosomal gene that is required for the expression of genes on the Y chromosome.
SRY is a gene present on the X chromosome that triggers female development.
An individual with an X and Y chromosome but a missing SRY gene will develop female
sex characteristics.
Correct:
SRY is a gene region present on the Y chromosome that triggers male development.
An individual with an X and Y chromosome but a missing SRY gene will develop female
sex characteristics.
Incorrect:
SRY is an autosomal gene that is required for the expression of genes on the X chromosome.
SRY is an autosomal gene that is required for the expression of genes on the Y chromosome.
SRY is a gene present on the X chromosome that triggers female development.
The gene responsible for X-inactivation is
XIST
You are working as a cytogeneticist (a scientist who looks for and evaluates chromosomal
and genetic abnormalities) and you have been asked to look at cell samples from a woman
who is experiencing infertility. You first stain the cells to look for Barr bodies and you find
that she has two Barr bodies in each cell. Which of the following is a possible conclusion
about her sex chromosomes?
She is genotype XXX.
, She has only a single X chromosome.
She is XXY with a non-functional Y chromosome.
She is genotype XX.
She is genotype XXX.
A person with Turner's Syndrome only has a single X sex chromosome. Which of the following
must be true of a person with Turner's syndrome? Select all that apply.
This person is most likely phenotypically female.
This person is most likely phenotypically male.
This person will have Barr bodies in their cells.
This person will not have Barr bodies in their cells.
This person will have 46 chromosomes in their body
cells. This person will have 45 chromosomes in their
body cells. Correct:
This person is most likely phenotypically female
This person will not have Barr bodies in their cells.
This person will have 45 chromosomes in their body cells.
Incorrect:
This person is most likely phenotypically male.
This person will have Barr bodies in their cells.
This person will have 46 chromosomes in their body cells.
Males are more often affected by sex-linked traits than females because
