In the Meselson-Stahl experiment, bacterial DNA was labeled completely with heavy nitrogen (15N) and then grown
in the presence of light nitrogen (14N). When only mixed DNA was observed after ONE generation of growth in 14N,
what was the conclusion?
a. DNA replication is semiconservative
b. DNA replication is conservative
c. DNA replication is dispersive
d. DNA replication is either semiconservative or dispersive
e. DNA replication is either semiconservative or conservative
ANSWER: d
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A researcher discovers a new, single-celled bacterium very similar to Thiomargarita namibiensis. At first he is confused because this organism is quite large compared to other bacteria
He also knows that because of diffusion, most bacterial cells don't exceed 1m in size. What might the researcher notice about the internal structure of his new bacterium? (Select all correct choices.) A. It contains several membrane-bound organelles, facilitating the diffusion of molecules. B. It contains several large histones, facilitating the diffusion of molecules. C. It is completely filled by cytoplasm, limiting the distance molecules need to diffuse. D. It contains a large vacuole, limiting the distance molecules need to diffuse.
Vision in toothed whales is very strong
Indicate whether the statement is true or false
The most abundant molecules in cells are
a. proteins. b. carbohydrates. c. minerals. d. water.
Annelids possess all of the following except
A. adductor muscles. B. ganglia to respond to light and respond to other environmental cues. C. setae in each segment. D. circulatory, excretory, and neural elements in each segment. E. muscles to swim, crawl, and burrow.