genetics lecture UCF PCB 3063 test 1 Questions and Answers Fully Solved
Males produce relatively small gametes; females produce larger gametes. - Answers What is considered
to be the fundamental difference between males and females of most organisms?
In the XX-XO sex determination system, females have two copies of the sex-determining chromosome,
whereas males have only one copy. Males must be considered heterogametic because they produce two
different types of gametes with respect to the sex chromosome: either containing an X or not containing
an X. - Answers Describe the XX-XO system of sex determination. In this system, which is the
heterogametic sex and which is the homogametic sex?
In the XX-XY system, males are heterogametic and produce gametes with either an X chromosome or a Y
chromosome. In the ZZ-ZW system, females are heterogametic and produce gametes with either a Z or a
W chromosome. - Answers How does sex determination in the XX-XY system differ from sex
determination in the ZZ-ZW system?
In organisms that follow this system, there is no cytogenetically recognizable difference in the
chromosome contents of males and females. Instead of a sex chromosome that differs between males
and females, alleles at one or more loci determine the sex of the individual. - Answers What is meant by
genic sex determination?
Turner syndrome: XO
Klinefelter syndrome: XXY (rarely XXXY, XXXXY, or XXYY) Androgen insensitivity: XY
Triplo-X females: XXX - Answers Give the typical sex chromosome complement found in the cells of
people with Turner syndrome, with Klinefelter syndrome, and with androgen-insensitivity syndrome.
What is the sex-chromosome complement of triplo-X females?
Males show the phenotypes of all X-linked traits, regardless of whether the X-linked allele is normally
recessive or dominant. Males inherit X-linked traits from their mothers, pass X-linked traits to their
daughters, and through their daughters to their daughters' descendants, but not to their sons or their
sons' descendants. - Answers What characteristics are exhibited by an X-linked trait?
Y-linked traits appear only in males and are always transmitted from fathers to sons, thus following a
strict paternal lineage. Autosomal male-limited traits also appear only in males, but they can be
transmitted to boys through their mothers. - Answers What characteristics are exhibited by a Y-linked
trait?
Tortoiseshell cats have two different alleles of an X-linked gene: X+ (non-orange, or black) and Xo
(orange). The patchy distribution results from X-inactivation during early embryo development. Each cell
of the early embryo randomly inactivates one of the two X chromosomes, and the inactivation is
maintained in all of the daughter cells. So each patch of black fur arises from a single embryonic cell that
inactivated the Xo, and each patch of orange fur arises from an embryonic cell that inactivated the X+.
Normal male cats have only one X chromosome, so they cannot have patches of black and orange fur. -
, Answers Explain why tortoiseshell cats are almost always female and why they have a patchy
distribution of orange and black fur.
a. Female
b.Male
c. Male
d. female
e. Male (Klinefelter syndrome)
In humans, a single functional copy of the SRY gene, normally located on the Y chromosome, determines
phenotypic maleness by causing gonads to differentiate into testes. In the absence of a functional SRY
gene, gonads differentiate into ovaries and the individual is phenotypically female. - Answers For each of
the following chromosome complements, what is the phenotypic sex of a person who has
a. XY with the SRY gene deleted?
b. XX with a copy of SRY gene on an autosomal chromosome?
c. XO with a copy of SRY gene on an autosomal chromosome
d. XXY with the SRY gene deleted?
e. XXYY with one copy of the SRY gene deleted
her mothers mother: no
Males produce relatively small gametes; females produce larger gametes. - Answers What is considered
to be the fundamental difference between males and females of most organisms?
In the XX-XO sex determination system, females have two copies of the sex-determining chromosome,
whereas males have only one copy. Males must be considered heterogametic because they produce two
different types of gametes with respect to the sex chromosome: either containing an X or not containing
an X. - Answers Describe the XX-XO system of sex determination. In this system, which is the
heterogametic sex and which is the homogametic sex?
In the XX-XY system, males are heterogametic and produce gametes with either an X chromosome or a Y
chromosome. In the ZZ-ZW system, females are heterogametic and produce gametes with either a Z or a
W chromosome. - Answers How does sex determination in the XX-XY system differ from sex
determination in the ZZ-ZW system?
In organisms that follow this system, there is no cytogenetically recognizable difference in the
chromosome contents of males and females. Instead of a sex chromosome that differs between males
and females, alleles at one or more loci determine the sex of the individual. - Answers What is meant by
genic sex determination?
Turner syndrome: XO
Klinefelter syndrome: XXY (rarely XXXY, XXXXY, or XXYY) Androgen insensitivity: XY
Triplo-X females: XXX - Answers Give the typical sex chromosome complement found in the cells of
people with Turner syndrome, with Klinefelter syndrome, and with androgen-insensitivity syndrome.
What is the sex-chromosome complement of triplo-X females?
Males show the phenotypes of all X-linked traits, regardless of whether the X-linked allele is normally
recessive or dominant. Males inherit X-linked traits from their mothers, pass X-linked traits to their
daughters, and through their daughters to their daughters' descendants, but not to their sons or their
sons' descendants. - Answers What characteristics are exhibited by an X-linked trait?
Y-linked traits appear only in males and are always transmitted from fathers to sons, thus following a
strict paternal lineage. Autosomal male-limited traits also appear only in males, but they can be
transmitted to boys through their mothers. - Answers What characteristics are exhibited by a Y-linked
trait?
Tortoiseshell cats have two different alleles of an X-linked gene: X+ (non-orange, or black) and Xo
(orange). The patchy distribution results from X-inactivation during early embryo development. Each cell
of the early embryo randomly inactivates one of the two X chromosomes, and the inactivation is
maintained in all of the daughter cells. So each patch of black fur arises from a single embryonic cell that
inactivated the Xo, and each patch of orange fur arises from an embryonic cell that inactivated the X+.
Normal male cats have only one X chromosome, so they cannot have patches of black and orange fur. -
, Answers Explain why tortoiseshell cats are almost always female and why they have a patchy
distribution of orange and black fur.
a. Female
b.Male
c. Male
d. female
e. Male (Klinefelter syndrome)
In humans, a single functional copy of the SRY gene, normally located on the Y chromosome, determines
phenotypic maleness by causing gonads to differentiate into testes. In the absence of a functional SRY
gene, gonads differentiate into ovaries and the individual is phenotypically female. - Answers For each of
the following chromosome complements, what is the phenotypic sex of a person who has
a. XY with the SRY gene deleted?
b. XX with a copy of SRY gene on an autosomal chromosome?
c. XO with a copy of SRY gene on an autosomal chromosome
d. XXY with the SRY gene deleted?
e. XXYY with one copy of the SRY gene deleted
her mothers mother: no
