Xeroderma pigmentosum is caused by
a. a thymine dimer.
b. a translocation.
c. a deletion.
d. an inversion.
e. a duplication.
A
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Biological nitrogen fixation is carried out ________.
A. only by a limited number of prokaryotes B. only in totally anaerobic environments C. only by prokaryotes in symbiotic relationships with plants D. by prokaryotes and some protists
Ribosomal subunits
a. come together in threes to form functional units. b. are composed of mRNA and structural proteins. c. are synthesized in the cytoplasm. d. converge with tRNA when mRNA is to be translated. e. are transcribed from the complementary strand of DNA that is used for tRNA transcription.
Which of the following ions is significantly involved in the opening and closing of the stomata?
(A) Calcium (B) Nitrogen (C) Potassium (D) Magnesium
Which of the following statements is true of reptiles?
A. Sperm are released in the vicinity of the female. B. Eggs have an amnion and a chorion. C. Eggs undergo external fertilization. D. Larvae become adults by metamorphosis. E. Embryonic and fetal development in all species is only by oviparity.