At several points in the cell cycle there are checkpoints that control the cell's passage from one phase to the next. If a cell receives a signal at each checkpoint, it continues to the next phase; if it does not receive the signal, the cell does not
continue. For example, a growth factor may stimulate a cell to move from G1 into S phase. If no growth factor is present, the cell cycle stops in G1 and the cell does not divide. Predict what would happen to a cell and to a multicellular organism if there was a defect at the checkpoint and the cell continued through the cell cycle even in the absence of a signal.
What will be an ideal response?
If a cell cycle checkpoint is defective, then the cell will continue to divide even when it's not supposed to. This is uncontrolled cell division. In a multicellular organism this would lead to abnormal growths of cells, producing tumors and cancer.
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Discuss Sir Francis Galton’s contribution to genetics and identify the important concept that is linked to his
observations.What will be an ideal response?
Potassium ions are important in the resting membrane potential and the action potential of the nerve and to the contraction of muscle cells. The concentration gradient of potassium ions is critical to both
An excess of potassium outside a neuron or muscle cell would negate the concentration gradient. What would happen if the heart were injected with massive amounts of potassium? Explain your answer.
The molecule serving as mRNA can be incorporated in the newly synthesized virus capsids of all of the following except
a. 1 strand RNA picornaviruses. b. 1 strand RNA togaviruses. c. 2 strand RNA rhabdoviruses. d. double-stranded RNA reoviruses. e. Rotavirus.
The biological diversity encountered increases as one moves from the poles to the tropics. Within a particular latitude, diversity also varies:
A) between different continents B) between different habitats C) as a function of temperature and precipitation D) as a function of topographic complexity E) all of the above