Which of the following is not good direct evidence that the cell-cycle control system is conserved through billions of years of divergent evolution?
(a) A yeast cell lacking a Cdk function can use the human Cdk to substitute for its missing Cdk during the cell cycle.
(b) The amino acid sequences of cyclins in plants are similar to the amino acid sequences of cyclins in humans.
(c) The Cdk proteins in humans share conserved phosphorylation sites with the Cdk proteins in yeast.
(d) Yeast cells have only one Cdk, whereas humans have many Cdks.
(d) Although it is true that yeast cells have one Cdk and human cells have many, this statement does not provide any evidence for the conservation of function across evolutionary time. All the other statements do provide such evidence.
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Estuaries are immune from larger temperature variations
Indicate whether the statement is true or false
If you cross RrYy and RRyy pea plants, what fraction of the offspring will have yellow peas? R = round, r = wrinkled, Y = yellow, y = green.
A. 100% B. 50% C. 75% D. 25% E. 0%
The acetylcholine receptor is a ligand-gated channel that produces
A. Depolarization by allowing K+ ions to leave the muscle fiber. B. Depolarization by allowing Cl- ions to enter the muscle fiber. C. Depolarization by allowing Na+ ions to enter the muscle fiber. D. Hyperpolarization by allowing Na+ ions to exit the muscle fiber. E. Repolarization by activating second messenger systems within the muscle fiber.
Most of the ocean’s productivity occurs
a. in the open ocean b. in the intertidal zone. c. in the neritic zone. d. near hydrothermal vents. e. in the benthic province.