The basic unit of a DNA molecule is the
A. nitrogenous base.
B. sugar-phosphate backbone.
C. amino acid.
D. nucleotide.
E. ribose sugar.
D
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If Escherichia coli is cultured in broth containing both glucose and lactose, it
A. uses lactose preferentially until the supply is exhausted, then uses glucose. B. uses glucose preferentially until the supply is exhausted, then uses lactose. C. uses only the glucose (it cannot use lactose as a source of carbon). D. uses glucose and lactose simultaneously.
Compared with the trans-Golgi proteins, the cis-Golgi proteins would
A) be identical. B) be shorter in length. C) be glycosylated and contain amino acid modifications. D) contain sialic acid. E) be glycosylated only.
At the start of translation the initiator tRNA is base paired with the start codon at ____ in the
ribosome.
a. the A site (aminoacyl site) b. first the A site (aminoacyl site) and then the E site (exit site) c. the P site (peptidyl site) d. first the A site (aminoacyl site) and then the P site (peptidyl site) e. the E site (exit site)
The human papilloma virus E6 and E7 genes exemplify:
A. tumor suppressor genes B. oncogenes C. protooncogenes D. CDK inhibitors E. cyclin-dependent kinases