The proteobacterium Rhizobium lives in a close association with legume roots, providing a source of nitrogen for the plant. In return, the plant provides Rhizobium with food produced by photosynthesis. In this relationship, Rhizobium is an example of a(n):
A. parasite
B. producer
C. pathogen
D. mutualist
E. methanogen
Answer: D
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Two 6-base sequences are present in bacterial promoters: TATAAT (located 10 nt upstream from the start site) and TTGACA (located 35 nt upstream from the start site). What is the significance of the fact that these two base sequences are different?
A. Binding sites for both the holoenzyme and ATP are provided. B. Both the location of the start site and the direction of transcription can be established. C. Binding sites for both the core polymerase and holoenzyme are provided. D. The transcription bubble can be properly formed. E. It allows RNA polymerase to distinguish between the template strand and the coding strand of the DNA molecule.
If a set of genes is repressed in the presence of the controlling substance, it is referred to as ________ control.
Fill in the blank(s) with the appropriate word(s).
Signaling by cadherins is an example of _______ signaling.
a. autocrine b. endocrine c. paracrine d. direct cell-to-cell
Choose the most appropriate description for each item.
A. B. Nucleotides C. Phospholipids D. Enzymes