The base composition in DNA isolated from cow liver cells is 28% adenine; what percent of the bases are cytosine?
A) 14%
B) 22%
C) 28%
D) 36%
E) 56%
Answer: B
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A microbe is discovered growing near a deep sea thermal vent. When researchers bring a sample up to the surface and try to grow it in a lab at room temperature in a normal incubator, they are unsuccessful. Why?
A. The pressure isn't the same at sea level as it is on the ocean floor. B. Oxygen concentrations are very different between the two environments-it's possible the microbe is a strict anaerobe and is poisoned by the air (oxygen) in the lab. C. Salt concentrations might be different in the media the researchers are attempting to use and the salt water the microbe is used to living in. This might be causing osmotic pressure differences that the microbe can't tolerate. D. The temperature is probably different-the thermal vent would be very hot, while these researchers are trying to grow this microbe at room temperature. The enzymes in the cells are probably outside of their normal operating range at room temperature, and therefore nonfunctional. E. All of the above.
Which of these is a reasonable definition of a gene based on current understanding of biology?
A prediabetic individual would have a fasting glucose measurement (mg/dL) above ____
a. 20 b. 50 c. 75 d. 100 e. 110
In open-water marine ecosystems, the ________ occupy the same trophic level as the giant sequoias (redwoods) in the forests of California
A) fast-swimming, fish-eating tuna B) giant, squid-eating whales C) microscopic bacteria that decompose all the other organisms once they have died D) tiny, multicellular zooplankton ("animal drifters") that feed on phytoplankton E) microscopic, single-celled algae (protists) called phytoplankton ("plant-like drifters")