How does the age of the mother seem to correlate with the incidence of genetic birth defects?
a. Defect incidence sometimes increases and sometimes decreases with increasing age.
b. Defect incidence decreases with increasing age.
c. Defect incidence increases with increasing age.
d. Defect incidence has no correlation to age.
Answer: c. Defect incidence increases with increasing age.
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A plasmid vector and chromosomal DNA are treated separately with the same restriction enzyme. Which of the following might occur if the digested plasmid and chromosomal DNA were incubated together?
A. The two sticky ends of the plasmid could hybridize back together, recircularizing. B. The two sticky ends of the plasmid could hybridize to both sticky ends of the chromosomal DNA fragments. C. The two sticky ends of the plasmid could hybridize back together and recircularize as well as hybridize to both ends of a fragment of chromosomal DNA. D. The two sticky ends of the plasmid could hybridize with two ends of another type of plasmid. E. The two sticky ends of the vector would remain free or unhybridized.
New genes are thought to arise by which mechanism?
A) Gene duplication followed by divergence due to mutation. B) Fusion of two genes due to mating between individuals of two different species. C) Conversion of introns to exons by the accumulation of mutations. D) Mutation of a DNA sequence activates a gene that was previously turned off.
In a neuron, a graded potential:a
does not vary in magnitude. b. becomes stronger as it propagates. c. only generates slow action potentials. d. fades out within a few millimeters. e. propagates only along unmyelinated axons.
The introduction of a few individuals into a new habitat that is unoccupied by other members of the species is a(n)
A) temporal isolation. B) founder event. C) adaptive radiation. D) limited speciation. E) extinction.