In the Watson and Crick model of DNA, the "steps" of the ladder are composed of
A. a purine and a pyrimidine.
B. a sugar and a phosphate molecule.
C. two purines.
D. two pyrimidines.
E. sugars.
Answer: A
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Collectively, what did the work of Charles Darwin, Francis Darwin, and Fritz Went demonstrate about phototropism in plants? Select all correct choices
A. A chemical signal is produced in shoot tips in response to light. B. A chemical signal is produced in shoot stems in response to light. C. Cells exposed to a chemical signal produced by light will grow (elongate). D. Cells exposed to a chemical signal produced by light will not grow (elongate).
The first fish:a
were small and jawless but had bony armor. b. appeared about 2 billion years ago. c. were the lobe-finned fish. d. appeared in the Silurian period. e. developed in the Precambrian period.
Describe the similarities and differences observed among phototrophic bacteria
What will be an ideal response?
In tobacco plants, a H+/sugar cotransporter called NtSUT1 is required for sucrose loading into phloem. Levels of NtSUT1 are likely to be highest in what plant tissue?
A. roots B. leaves C. flowers D. seeds