Ethyl methane sulfonate （EMS） is a kind of _____ which can cause base mutation on DNA strands（）
A. base analog
B. base modifier
C. intercalating agent
D. Physical mutagens
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Which frequently lead to the formation of thymine dimers in the DNA chain（）
A. Intercalating agents
B. Ultraviolet radiation
C. Base analogs
D. Nitrite
When bacterial replication introduces a mismatch into double stranded DNA, the mismatch repair system（）
A. changes both the parental strand and the newly synthesized strand
B. corrects the mismatch by changing the newly synthesized unmethylated strand
C. corrects the mismatch by changing the parental strand
D. corrects the strand which is methylated
Okazaki fragments are（）
A. the smallest subunits of DNA polymerase III
B. short stretches of DNA formed on the lagging strand
C. short RNA primers needed for initiation of polymerization
D. fragments of DNA polymerase I that lack 5′ → 3′ exonuclease activity
The elongation of the lagging strand during DNA synthesis（）
A. In the 3’ to 5’ direction
B. Produces Okazaki fragments
C. Polymerizes in the direction of fork movement
Does not require a template strand
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