a. initiates the X inactivation process in females.
b. It is located on the X chromosome and causes the X to pair with the Y chromosome during male meiosis.
c. t is located on the Y chromosome and initiates the developmental pathway toward the male phenotype.
d It is located on an autosomal chromosome and represses expression of autosomal genes in order to balance their expression level with genes on the X chromosome.
Which of the following chromosome constitutions would never lead to a viable human baby being born?
c. XO (O = the absence of a second chromosome)
In species of birds, males are the homogametic sex and females the heterogametic sex. Which if the following is true in this system of sex determination?
a. The gender of the offspring is determined by the female parent.
b. Male offspring have a ZW chromosome constitution.
c. The gender of the offspring is determined by the male parent.
d. Female offspring have a ZZ chromosome constitution.
In a germ-line cell from a human male that is dividing, when do the X and Y chromosomes segregate?
a. During mitosis
b. During meiosis I, anaphase
c. During meiosis II, anaphase
d. They do not segregate; gametes contain a copy of X and a copy of Y.
What is the sex chromosome constitution of a male duck-billed platypus?
An XXY chromosome constitution produces ________ development in humans and _________ development in fruit flies.
a. female; female
b. male; male
c. female; male
d. male; female
e. male, intersex
Human males, with XY chromosomes are___________ and produce two different kinds of gametes, whereas females with XX chromosomes are ___________ and produce only one kind.
a. homogametic; heterogametic
b. dioecious; monoecious
c. heterogametic; homogametic
d. monoecious; dioecious
e. monoecious; heterogametic
In which of the following phenotypic females do testes develop?
a. XY with an deletion that removes the SRY gene
c. XY with the X-linked recessive condition of androgen insensitivity syndrome
e. Both a and b are correct.
During the evolution of the human Y chromosome, all of the following are assumed to occur EXCEPT
c. many of the genes on the original ancestral chromosome suffered mutations and became inactive during the evolution of the Y chromosome.
d. many of the genes on the early X chromosome that were responsible for critical cellular functions got moved to the evolving Y chromosome.
e. several palindromic regions evolved or were acquired and are now present on the Y chromosome.
Red-green color blindness is X-linked recessive. A woman with normal color vision has a father who is color blind. The woman has a child with a man with normal color vision.Which phenotype is NOT expected?
a. A color-blind female
b. A color-blind male
c. A noncolor-blind female
d. A noncolor-blind male
If a male bird that is heterozygous for a recessive Z-linked mutation is crossed to a wild type female, what proportion of the progeny will be mutant males?
A Barr body is a(n):
a. gene on the X chromosome that is responsible for female development.
b. patch of cells that has a phenotype different from surrounding cells because of variable X inactivation.
c. inactivated X chromosome, visible in the nucleus of a cell that is normally from a female mammal.
d. extra X chromosome in a cell that is the result of nondisjunction.
1. What is the apparent purpose for X inactivation in humans and other mammals?
a. It allows for the levels of expression of genes on the X chromosome to be similar in males and females.
b. It allows for the levels of expression of genes on the autosomes to be similar to the levels of genes on the X chromosome.
c. It suppresses the expression of genes on the Y chromosome in males.
In which of the following individuals would you expect to find two Barr bodies in their somatic cells?
a. The Y chromosome has higher gene expression
b. The Y chromosome has lower gene expression levels when two X chromosomes are present compare to one X. c. Some genes remain active on inactive X chromosomes so XXY males would produce have higher expression levels for these genes compared to XY males.