What evidence supports the idea that some nuclei are totipotent?
a. Nuclei taken from the cells of an embryonic frog can direct a frog egg to develop into a tadpole.
b. Nuclei taken from the cells of a frog embryo can direct any amphibian egg to develop into a tadpole.
c. Nuclei taken from a different species can direct a tadpole egg to develop into a normal tadpole.
d. Some cells are capable of undergoing unlimited cell cycles.
e. Some cells are capable of arresting their cell cycle at will.
a
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Researchers discovered an enzyme in HIV called protease. Once the enzyme's structure was known, researchers began looking for drugs that would fit into the active site and block it
HIV is the virus that causes AIDS. In the mid-1990s, A) vaccination B) denaturation C) allosteric regulation D) competitive inhibition
Animal cells are permeable to water and urea but NOT to sucrose. Initially, the inside of a cell contains 1 M sucrose and 1 M urea and the outside 1 M sucrose and 2 M urea. After the system reaches equilibrium, what changes are observed?
A. The molarity of urea would be higher outside than inside the cell. B. The molarity of sucrose would be similar inside and outside the cell. C. Water would move out of the cell causing the cell to shrivel. D. The molarity of urea would be higher outside the cell and the molarity of sucrose would be similar inside and outside the cell. E. The molarity of sucrose would be similar inside and outside the cell and water would move out of the cell causing the cell to shrivel.
A water-soluble hormone (signaling molecule) would most likely bind to which membrane protein?
a. active transporter b. recognition c. receptor d. passive transporter e. regulator
The hobbit-sized hominin whose fossilized remains were recently discovered on a remote oceanic island belonged to the species
A) Homo erectus. B) Homo floresiensis. C) Homo neanderthalensis. D) Homo sapiens. E) Homo habilis.