The methylation of GATC sequences in E. coli（）
A. is performed by the dam methylase
B. is delayed for ~10 min after DNA synthesis
C. is related to the initiation of DNA replication
D. all of the above
Sometimes deaminated bases must be removed from DNA because（）
A. they denaturate the molecule
B. they form thymine dimers
C. they pair incorrectly during replication
D. the mRNA formed may be irregular
Deletion of 4 bases from the coding region of a gene will give（）
A. nonsense mutations
B. missense mutations
C. silent mutations
D. frameshift mutations
A major difference between prokaryotic and eukaryotic DNA replication mechanisms is（）
A. no Okazaki fragments are made in eukaryotes
B. both leading and lagging strands are continuous in eukaryotes
C. no primer synthesis is needed in eukaryotes
D. the replication fork moves slower in eukaryotes
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