Which one of the following is nottrue of tRNA molecules?
A. tRNA molecules are single-stranded RNA.
B. The 3'-terminal nucleotide of tRNA is the site of amino acid attachment.
C. The anticodon arm of tRNA contains a three nucleotide sequence that is identical to a specific mRNA codon.
D. tRNA molecules contain the unusual nucleotides dihydrouridine, pseudouridine, and ribothymine.
How is initiation at oriC regulated in bacteria?
A. SeqA binds to hemimethylated DNA and sequesters the newly replicated origin.
B. DnaA-ADP, formed when DnaA hydrolyzes its ATP, cannot maintain the destabilization of the origin so the closed complex reforms.
C. The Hda protein binds the clamp causing DnaA to hydrolyze its ATP.
D. RNA polymerase activity produces superhelical twisting that promotes melting of the origin by DnaA.
E. All of these choices are correct.
The isoelectric point (pI) is:
A. the pH at which a protein has a net positive charge.
B. the pH at which a protein has a net negative charge.
C. the pH at which a protein has a net charge of zero.
D. the distance a protein having a positive charge will travel in gel electrophoresis.
E. the distance a protein having a negative charge will travel in gel electrophoresis.
What is the sequence of the last three nucleotides of all mature tRNA molecules?
A. ACC
B. CCA
C. TGG
D. GGT
Salmonella typhimurium can change flagellar proteins to evade immune response by host systems. What is this process called?
A. lysogeny
B. bacterial transduction
C. phase variation
D. transposition
E. cointegration
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