Explain how X inactivation can result in female mosaicism and give examples What will be an ideal response?
ANSWER: Female mammals are constructed of two different cell types. Some cells express alleles from
the father’s X chromosome and some cells express alleles from the mother’s X chromosome.
Early in embryonic development, one X chromosome in each cell will be inactivated. The
inactivation will occur randomly. If a visible trait is linked to an inactivated X chromosome,
any cells derived from the original inactivated cell will not display the trait. The pattern of
coat color in some mice and in some cats, and the patches of affected and unaffected skin on
a woman with anhidrotic ectodermal dysplasia represent groups of cells descended from a
single cell in which the inactivation event occurred
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Major evolutionary changes have resulted in anatomical and physiological adaptations that optimize the rate of gas exchange in animals by each of these factors except ________.
A. decreasing the distance for diffusion B. increasing the diffusion constant for each gas C. increasing the surface area for diffusion D. increasing the concentration difference driving diffusion
Osmosis can be characterized as: a. associated with an organism's salinity
b. a very important and challenging part of a marine organism's survival. c. all of these choices. d. the movement of water across a membrane due to solute concentrations.
A cell in the G2 phase:a
has twice the amount of DNA present in a telophase nucleus.
b. has visibly distinct chromosomes. c. lacks a visible nuclear membrane. d. is in mitosis. e. is in cytokinesis.
Three loci, mitochondrial malate dehydrogenase that forms a and b (MDHa, MDHb), glucuronidase that forms 1 and 2 (GUS1, GUS2), and a histone gene that forms + and ? (H+, H?), are located on chromosome #7 in humans. Assume that the MDH locus is at
position 35, GUS at position 45, and H at position 75. A female whose mother was homozygous for MDHa, GUS2, and H+ and whose father was homozygous for MDHb, GUS1, and H? produces a sample of 1000 egg cells. Give the expected numbers of the MDHa GUS2 H? cells she would produce. Assume no chromosomal interference. A) 15 B) 135 C) 315 D) 0 E) 235