Carriers of cystic fibrosis have some protection against intestinal infections such as cholera. However, people with two copies of the cystic fibrosis allele develop a life-threatening disease. The mutant allele is very common in people of northern European descent because of
A. disruptive selection.
B. directional selection.
C. artificial selection.
D. sexual selection.
E. stabilizing selection.
Answer: E. stabilizing selection.
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Which enzyme links nucleotides into a new stand of DNA?
a. DNA ligase b. DNA mutase c. DNA polymerase d. DNA primer e. DNA replicase
In humoral immunity, cells that are produced by activated B cells and function by secreting antibodies are called
A. cytotoxic T cells. B. helper T cells. C. plasma cells. D. macrophages. E. memory cells.
A ________ is one who believes that major evolutionary change happens, or can happen, by large "jumps" or bursts, such as mutations with large effects
Fill in the blank(s) with correct word
Today, gene swapping between two species is
A. infrequent but possible; it happened more often in the distant past. B. much more frequent compared to in the distant past. C. impossible, but it happened frequently in the distant past. D. only possible if they are in the same family of organisms, such as lions and tigers.