Nerve impulses travel along neurons by the opening of channels that allow sodium ions to flow inward, followed by an outward flow of potassium ions
In order to ensure that the impulse may be produced at any time, sodium is actively transported out of the cell and potassium is transported into the cell by the sodium/potassium pump. Which of the following types of work is performed by the sodium/potassium pump?
A) mechanical
B) electrical
C) concentration
D) synthetic
E) bioluminescent
Answer: C
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Which statement describes the fern life cycle?
a. Gametophytes originate within, and are dependent upon, sporophytes b. Sporophytes originate within, and are dependent upon, gametophytes c. Both gametophytes and sporophytes are totally independent from each other and are equally dominant d. Gametophytes are free-living and photosynthetic, but are replaced by a dominant sporophyte generation e. Gametophytes are photosynthetic and partially independent from the sporophytes
Homologous recombination occurs in a heterozygote in which alleles D and d differ by a single base pair. The D allele has a G at one position, whereas the d allele has a C at the same position. If branch migration causes heteroduplex formation across this position, what is the expected outcome?
A) Both D and d alleles will remain unchanged because G can base pair with C. B) Mismatch repair will identify an abnormal G-G base pair and may convert the D allele to a d allele. C) Mismatch repair will identify an abnormal C-G base pair and will ensure that the cell has two copies of each allele. D) Mismatches will cause the Holliday junction to be unstable and to resolve by the noncrossover pathway.
People carrying less than 35 CAG trinucleotide repeats are more likely to develop Huntington disease. Indicate whether the statement is true or false
When experimental plants (e.g., Atriplex prostrata) were grown at high densities,
A) individual growth rates increased. B) the proportion of resources allocated to leaf production increased. C) individual plant weight increased. D) net photosynthetic rate increased.