The amino acids valine and threonine differ only by the presence of a hydroxyl group or a methyl group
The aminoacyl-tRNA synthetases for tRNAVal and tRNAThr must discriminate between using these two very structurally similar amino acids as substrate for creating charged tRNAs. The discrimination by the Valyl-tRNA synthetase is by differential binding of valine and/or threonine to a first site on the synthetase and, then, differential binding to a second site on the synthetase. This is an example of what known process in the specificity of tRNA synthetases?
A. adenylation
B. kinetic proofreading
C. wobble
D. premature termination
E. accommodation
B
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The constructive phase of coral reef formation involves:
a. consumption of soft corals by crown of thorns sea stars. b. settling of planula larvae. c. Halimeda growth. d. both a and c
Currently, two extant elephant species (X and Y) are placed in the genus Loxodonta, and a third species (Z) is placed in the genus Elephas. Thus, which statement should be true?
A. Species X and Y are not related to species Z. B. Species X and Y share a common ancestor that is still extant (in other words, not yet extinct). C. Species X and Y are the result of artificial selection from an ancestral species Z. D. Species X and Y share a greater number of homologies with each other than either does with species Z. E. Species X, Y, and Z share a common ancestor, but nothing more can be claimed than this.
What can paleoecologists utilize to assess which tree species existed in an area?
A) climate models B) soil types C) DNA from current trees D) ancient pollen
A(n) ________ is an animal that carries a disease from one host to another
Fill in the blank(s) with correct word