Recent discoveries of microscopic fossils have extended the known history of life to about:
A. 1 billion years ago.
B. 2 billion years ago.
C. 3.5 billion years ago.
D. 4.5 billion years ago.
C
You might also like to view...
Which of the following statements about muscle proteins is false?
A. Actin filaments have globular heads. B. Thick filaments consist of parallel bundles of myosin molecules. C. Tropomyosin lies in a groove formed by the actin helices. D. Titin connects myosin filaments to the Z disc. E. Z discs are protein backbones that mark the boundaries of sarcomeres.
One similarity between DNA transposons and retrotransposons is that
A) during transposition, both go through an RNA form that is copied back into DNA. B) both can encode an enzyme required for mobilization. C) transposition results in movement of the original transposon to a different place in the genome. D) they both have poly-A segments at one end.
The procedure by which embryos produced during in vitro fertilization are tested for defects is called
a. chorionic villus sampling. b. preimplantation diagnosis. c. amniocentesis. d. fetoscopy. e. senescence.
Which choice is an example of "recombinant DNA"?
A) a bacterial plasmid combined with a human gene B) DNA that has been cut with a restriction enzyme C) DNA that has been amplified by PCR D) any DNA that has been removed from a cell