Voltage-gated channels contain charged protein domains, which are sensitive to changes in membrane potential. By responding to a threshold in the membrane potential, these voltage sensors trigger the opening of the channels
Which of the following best describes the behavior of a population of channels exposed to such a threshold?
(a) Some channels remain closed and some open completely.
(b) All channels open completely.
(c) All channels open partly, to the same degree.
(d) All channels open partly, each to a different degree.
(a) Individual channels are either completely open or completely closed. However, in a given population, there will be a mixture of open and closed channels.
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Which of the following events occurs to a territory-holding male zebra finch when he hears the song of
the male zebra finch that holds the neighboring territory?
a. Cells in the nucleus of his forebrain fire frequently. b. The territory-holding male flies out to drive off the neighboring male. c. Cells in the nucleus of his forebrain do not respond to the song of the neighboring male. d. Testosterone levels in his blood rise measurably. e. The territory-holding male initiates a ritualized threat display that may culminate in an expansion of his territory into the neighbor's land.
Cones are responsible for:a
night vision. b. the detection of movement. c. dim light vision. d. peripheral vision. e. the perception of fine detail
Some mutations do not affect an organism's phenotype. Other mutations cause minor changes, and still others cause major changes. Which is most likely to cause a major change in an organism's phenotype?
A) a substitution of a single base B) an insertion of three consecutive bases C) the deletion of one arm of a chromosome D) a deletion of two bases at the end of a gene
Sickle-cell anemia is caused by a mutation that changes the second nucleotide of the codon from GAG to GUG. This results in a change of the amino acid from glutamic acid to valine. If the mutation affected the third nucleotide of the codon and changed
GAG to GAU then the amino acid would change from a glutamic acid to aspartic acid. Would you predict this change to have the same effect? What will be an ideal response?