Oxygen gas produced during photosynthesis originates as:
a) oxygen atoms contained in water molecules.
b) oxygen atoms from a molecule of chlorophyll that is oxidized by a photon.
c) oxygen atoms released by the metabolism of carbohydrates.
d) oxygen molecules in the atmosphere.
e) oxygen atoms contained in carbon dioxide are released when the carbon is fixed.
Ans: a) oxygen atoms contained in water molecules.
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Which of the following is not a feature of the "torpedo" model for RNA polymerase II transcription termination?
A. Conformational changes occur in the Pol II elongation complex when elongation factors dissociate. B. RNA is cleaved downstream from the poly(A) site. C. Exonuclease degradation of RNA promotes Pol II release. D. Pol II remains associated with the DNA template after mRNA synthesis. E. All of the choices given are a feature of the "torpedo" model.
Mutation as a force in genetic diversity serves to
A. increase genetic diversity. B. rapidly change allele frequencies. C. maintain a genetic equilibrium. D. work against selection. E. do none of these.
Molecules that carry out transcription bind to this region of the DNA.
A. Exon B. Transcription site C. Promoter D. Initiator E. Ribosome
Rods and cones are located in the ____.
A. lens B. cornea C. pupil D. iris E. retina