RNA polymerase Ⅰ of eukaryotic cell catalizes the synthesis of ( ).
A. Pre-rRNA(45S-rRNA )
B. hnRNA
C. tRNA
D. 5S-rRNA
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Which vitamine is essential for methionine cycle?()
A. biotin
B. vitamine B12
C. vitamine B6
D. pyridoxal
Which one is the key enzyme in the ornithine cycle?()
A. arginase
B. argininosuccinate lyase
C. argininosuccinate synthetase
D. ornithine carbamoyl transferase
The product of replication is ( )
A. RNA
B. DNA
C. protein
D. dNTP
Which can carry one carbon unit in living organism?()
A. vitamine B12
B. folic acid
C. tetrahydrofolate
D. biotin
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