Which of the situations below will enhance microtubule shrinkage?
(a) addition of a drug that inhibits GTP exchange on free tubulin dimers
(b) addition of a drug that inhibits hydrolysis of the GTP carried by tubulin dimers
(c) addition of a drug that increases the affinity of tubulin molecules carrying GDP for other tubulin molecules
(d) addition of a drug that blocks the ability of a tubulin dimer to bind to ?-tubulin
(a) A drug that inhibits GTP exchange on free tubulin dimers will effectively decrease the available pool of GTP-bound tubulin dimers available for addition to microtubule ends, thus tipping the balance in favor of microtubule disassembly. A drug that inhibits hydrolysis of GTP carried by tubulin dimers [choice (b)] or that increases the affinity of GDP-bound tubulin dimers for each other [choice (c)] will stabilize growing microtubules. Blocking the ability of a tubulin dimer to bind to ?-tubulin will decrease the rate of new microtubule formation but should not enhance microtubule shrinkage [choice (d)].
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Assume a double crossover occurs in this pair of chromosomes that results in chromatids of the genotypes A b C and a B c. If the first crossover (the one between A and B) involves chromatids 1 (A B C) & 4 (a b c), which chromatids could be involved in the second crossover?
Consider a pair of homologous chromosomes heterozygous for three genes (e.g. A B C / a b c) during prophase I of meiosis. Let the sister chromatids of one homolog be numbered 1 and 2; and the sister chromatids of the other homolog be numbered 3 and 4. A) 1 & 2 B) 3 & 4 C) 1 & 3 D) 2 & 4 E) 1 & 4 F) 2 & 3
Trimming a shrub will make it become more bushy (have more lateral growth) primarily due to a
reduction in the amount of ____.
a. auxin b. ethylene c. abscisic acid d. gibberellin e. cytokinin
The difference between the gray and white matter of the cerebrum is that:a
gray matter makes up the core, while white matter makes up the cortex. b. gray matter contains dendrites, while white matter contains cell bodies. c. gray matter contains unmyelinated axons, while white matter contains cell bodies. d. gray matter contains cell bodies, while white matter mostly contains myelinated axons. e. gray matter is in the right hemisphere, while white matter is in the left one.
Theory predicts that communication between mutualistic species should be favored if such communication results in an increase of individual fitness in both species
Can the experiment displayed below determine whether communication results in a fitness advantage in Iri-domyrmex ants and imperial blue butterflies? a. Yes, the experiment tests whether caterpillars communicate with ants; communication would not evolve in the absence of a fitness advantage. b. Yes, ants that respond to butterfly pupa stridulations have a higher fitness. c. No, gain or loss of fitness is not tested in this experiment. d. No, only the ants' fitness is tested.