Why don't recessive alleles that cause severe disorders disappear from human populations?
a. new alleles can arise by mutation.
b. in heterozygotes, the dominant allele suppresses the recessive one but does not eliminate
its presence.
c. in heterozygotes, although the trait associated with the recessive allele is not
demonstrated, the allele may be passed on to offspring.
d. some recessive traits are not lethal nor do they interfere with reproduction.
e. all of these.
E
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When an error of mitosis or meiosis results in a diploid gamete, the gamete is said to be ____, which can result in
____.
a. reduced; allopolyploidy only b. reduced; autopolyploidy only c. unreduced; allopolyploidy only d. unreduced; autopolyploidy only e. unreduced; both allopolyploidy and autopolyploidy
Natural killer cells destroy target cells by
a. releasing antibiotics, which breakdown the cell membrane. b. releasing perforin, which creates holes in the cell membrane. c. releasing histamine, which signals other blood cells to aggregate. d. releasing lysozyme, which breaks down the cell wall. e. releasing antibodies, which break down the cell wall.
Which of the following diseases is NOT caused by an airborne virus?
a. chicken pox b. measles c. mumps d. scarlet fever
The cyclic path that involves both biological and chemical processes of an ecosystem is called a ________.
A. biogeochemical pathway B. complete pathway C. complementary pathway D. hydrological pathway