A mammalian female's
a. cells usually have multiple Barr bodies.
b. body is a mosaic for the X-linked traits she inherits.
c. Barr bodies are active in some cells.
d. Barr bodies are produced after puberty.
e. X-linked recessive genes are always expressed because of the deactivation of an X chromosome in each cell.
ANSWER: b
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All of the following events occur during T-dependent activation of a B cell EXCEPT
A. an antigenic fragment held within an MCH Class II molecule of a dendritic cell binds to a specific T cell receptor on a naïve T-helper cell. B. specific cytokines from the T helper cells stimulate maturation and complete activation of the antigen-stimulated B cell. C. antigen within MCH class II molecule is presented by B cell to an activated T helper cell. D. antigen binds to specific B cell receptor molecules. E. antigen bound to the B cell receptor is internalized and transferred to an MHC class II molecule which then moves to the plasma membrane. F. There are no exceptions. All of these events occur during T-depedent activation of B cells.
Why are organisms with an odd number of chromosome sets usually sterile?
A) Almost all gametes will have an unbalanced set of chromosomes. B) Chromosomes will fail to segregate independently during meiosis I. C) Chromosomes will fail to segregate independently during meiosis II. D) Because an odd number of chromosomal sets is present, meiosis will not occur at all.
You are working with a patient who thinks they have been poisoned. Their blood pressure is elevated and tissue biopsies of the patient's liver show extra sodium channels in the kidneys. You suspect that the patient has been given
A. epinephrine. B. aldosterone. C. follicle-stimulating hormone (FSH). D. insulin. E. testosterone.
Homologous chromosomes may swap segments of genetic information during which phase of
meiosis? a. metaphase I b. metaphase II c. prophase I d. prophase II e. anaphase I