Signal transduction is the process by which:
A. transcription factors bind to cis-regulatory
regions of DNA and either activate or repress
transcription.
B. a specific combination of transcription
factors determines the developmental
pathway in a cell or group of cells.
C. a single master gene, or signal, activates a
series of downstream genes that lead to cell
differentiation.
D. an extracellular molecule activates a
membrane protein, which in turn activates
molecules inside the cell.
E. None of these choices is correct.
D
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Boyle's law of gas behavior predicts that as the volume of the lungs _____, the pressure of gases within the lungs must ______.
A. increase, decrease B. increase, increase C. decrease, decrease D. increase, not change E. decrease, not change
Explain how using a combination of two antimicrobial drugs helps prevent the development of spontaneously resistant mutants
A. All drugs work synergistically with each other-that is, their combined effects are far greater than either could achieve individually. Two drugs together helps to eliminate microbes, even if they have developed spontaneous mutations that would confer upon them resistance to the drugs. B. It is highly unlikely that the microbe might spontaneously develop two specific mutations to resist the effects of a pair of drugs. As such, even if one drug is resisted by the microbe, the second drug will eliminate the mutated microbe, thus preventing the development of spontaneously resistant mutants overall. C. All drugs work antagonistically with each other-that is, their combined effects are far greater than either could achieve individually. Two drugs together helps to eliminate microbes, even if they have developed spontaneous mutations that would confer upon them resistance to the drugs. D. Drugs can also select for mutations that will enhance the activity of another drug. So, each of the paired drugs will help to select for spontaneous mutations that enhance the activity of the other drug in the pair.
Components of vertebrate plasma include
_____ water. _____ red blood cells. _____ white blood cells. _____ oxygen. _____ nutrients.
An adult male produces sperm continuously by meiotic division of cells lining what structure?
A. Malpighian tubules B. Fallopian tubules C. seminiferous tubules D. epididymis tubules E. vas deferens tubules