Which of the following viruses may cause a persistent viral infection?
A. Measles virus
B. Varicellovirus
C. Herpes simplex 1
D. HTLV-1
Ans: A. Measles virus
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How do scientists calibrate a molecular clock for a group of organisms with known nucleotide sequences?
A) They use radioactive isotopes to measure the age of DNA material directly. B) They graph the number of nucleotide differences against the dates of evolutionary branch points known from the fossil record. C) They analyze fossilized DNA of known age and compare its nucleotide sequences to modern DNA sequences.
In this phylogeny, the P species are from the Pacific side and the C species are from the Caribbean side of the Isthmus of Panama. What is the most likely cause of speciation?
a. sympatric speciation b. parapatric speciation c. allopatric speciation via dispersal across the Isthmus of Panama d. allopatric speciation via isolation when the Isthmus of Panama closed
The conformational change in opsin triggered by the absorption of light by retinal activates a G protein. What do G proteins do in the cell?
A. G proteins contribute to signal pathways. B. G proteins influence the activity of other proteins and enzymes in a cell. C. G proteins can trigger the synthesis of second messengers. D. All the answer options are correct.
Which of the following is not an example of symbiotic nitrogen fixation?
A. Anabaenea with a water fern B. Rhizobium with leguminous plants C. Azotobacter with certain photosynthetic protists D. Frankia with woody shrubs