Unlike DNA, which typically forms a helical structure, different molecules of RNA can fold into a variety of three-dimensional shapes. This is largely because ___________________
(a) RNA contains uracil and uses ribose as the sugar.
(b) RNA bases cannot form hydrogen bonds with each other.
(c) RNA nucleotides use a different chemical linkage between nucleotides compared to DNA.
(d) RNA is single-stranded.
Choice (d) is correct. Choice (a) is true, but is not the main reason why different RNA molecules can form different three-dimensional structures (although ribose does increase potential hydrogen-bonding potentials compared to deoxyribose). Choices (b) and (c) are untrue.
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The small region of an inactivated X chromosome that is not inactivated contains ____________________ homologous to those on the Y chromosome
Fill in the blank(s) with correct word
Sugar is conducted in solution through specialized cells known as:
a. fibers. b. companion cells. c. sieve tube elements. d. tracheids. e. vessels.
In the figure on the right, each point represents data on females from a different species of bird. In total, 10 species are represented. What can you infer about survival and clutch size?
A) Animals with high fecundity tend to live longer. B) High clutch sizes tend to produce animals with low survival. C) Animals with high fecundity tend not to live as long as animals with low fecundity. D) Animals with low survival tend to have low clutch sizes.
Animals that swim about freely are
A. plankton. B. benthic. C. nekton. D. zooplankton.