Researchers Pulsed Rapidly Dividing Cultured Cells for 30 Minutes with Radioactive

question 33

Multiple Choice

Researchers pulsed rapidly dividing cultured cells for 30 minutes with radioactive thymidine. The cells were then exposed to a solution containing non- radiolabeled thymidine. Cells were analyzed at 2- hour intervals. At the 2- hour time point, no cells appeared to be dividing. Only after 4 hours did some labeled cells appear to be in M phase. This result can be explained in the following way:

• A) The cells were arrested in a nondividing state because of the treatment and could not enter M phase until several hours after the label was removed.
• B) There seems to be a gap or a lag in the cell cycle, between the synthesis of DNA and cell division.
• C) Synthesis S) phase is lengthy-about 12 hours in most cell types-and the radioactive thymidine was not present long enough for most cells to be labeled.
• D) Cultured cells all divide at the same time, and none synthesized DNA during the 30- minute labeling period.

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Government-imposed maximums on the rent that landlords can charge tenants.

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A legally imposed maximum price on a good or service, usually set below the equilibrium price to keep the goods affordable for consumers.

Equilibrium Price

The cost at which the amount of a product or service being sought matches the amount available, resulting in a stable market.

Price Ceiling

A government-imposed limit on how high the price of a product can be charged in the market to protect consumers from excessive prices.