pRb is a major control element of the cell cycle. It normally becomes
A. Transcriptionally induced at the G1 checkpoint
B. Dephosphorylated at the G1 checkpoint
C. Phosphorylated at the G1 checkpoint
D. Phosphorylated at the G2 checkpoint
E. Transcriptionally induced at the G2 checkpoint
Ans: C. Phosphorylated at the G1 checkpoint
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Which of the following may form one colony?
A. A single bacterial cell B. A small clump of bacteria C. A short chain of bacteria D. All of the choices are correct.
Which of the major tissue types has shortening of cells (i.e., contraction) as its major function?
A. nervous B. muscular C. epithelial D. connective E. All of the choices are correct
The graph below shows a growth curve of E. coli growing in a defined medium containing equal molar amounts of glucose and lactose.
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Based on your knowledge of the regulation of the lac operon, the best explanation of these results is that
A) early on, due to the presence of lactose, the bacteria utilize the lac operon. Glucose is used later.
B) the bacteria are utilizing both sugars simultaneously.
C) the presence of glucose causes the formation of cAMP catabolic repressor protein (CRP) complexes, which shut down the lac operon until the glucose is used up.
D) glucose is used first. Once glucose becomes limiting, intracellular cAMP increases, forming cAMP-CRP complexes that activate the lac operon to use lactose.
E) none of the above
When light strikes the rod cell, it becomes ________ and glutamate release onto bipolar cells ________.
A. excited; increases B. depolarized; increases C. hyperpolarized; decreases D. hyperpolarized; increases E. depolarized; decreases