【正确答案】Because of anti-parallel nature of the two strands of DNA，if one runs 5'→3' left to right,the other must run 3'→5' left to right.But the DNA synthesizing part(DNA polymerase)of all natural replicating machines can make DNA in only one direction:5'→3'.Reiii Okazaki concluded that both strands could not replicate continuousy.DNA polymerase could theoretically make one strand(the leading strand)continuously in the 5'→3' direction,but the other one(the lagging strand)would have to be svnthesized discontinuously with the DNA being made in short pieces.Both strands are synthesized simultaneously toward the same direction as the fork movement.

【答案解析】[考点]semidiscontinuous replication of DNA。DNA复制的半不连续性是由日本学者冈崎等提出来的，旨在解释DNA复制时，两条反向平行链如何能够随着复制叉的移动同时同向被合成，后来用实验得到了证实。