Which of the following situations in not an example of directional selection?
a. Peppered moths in England
b. All of these are examples of directional selection.
c. Rock pocket mice in Arizona.
d. Antibiotic resistance in bacteria.
e. None of these are examples of directional selection.
b
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Explain the differences between receptor up-regulation and down-regulation including the conditions under which a
cell would use one rather than the other. What will be an ideal response?
Although the specific mechanism of RNA interference has not been fully defined, it involves
A. double-stranded RNA interference with DNA. B. double-stranded mRNA interference with DNA. C. double-stranded RNA interference with mRNA. D. double-stranded DNA interference with mRNA.
The human genome codes for 20,000 to 25,000 proteins, but any given cell might produce only 5,000 different proteins. How is this possible?
A) Not every cell has the machinery for transcription and translation. B) Genes are regulated so that not all genes are transcribed in all cells. C) Every cell contains a different fraction of the genome. D) All possible proteins are made in all cells, but those that are not needed are degraded. E) Some cells use introns to produce proteins, and some cells use exons.
A single B lymphocyte can recognize multiple antigenic determinants.
Answer the following statement true (T) or false (F)