生物技術概論～遺傳學單元～ＤＮＡ複製增長的方向

For the question, it should be B, going 5' to 3'. Most biological processes go from 5' to 3'.

But in actuality, while DNA polymerase goes from 5' to 3', the DNA itself has both strands being replicated at roughly the same time. This involves the Okazaki fragment. It is better if you just look at a picture, which can be found here:

http://upload.wikimedia.org/wikipedia/commons/9/9f/DNA_replication.svg

(sorry I don't know how to post pictures directly here).

2008-10-02 09:56:25 補充：
為何一股可連續複製, 一股不行
This is definitely easier to explain with a picture. But when DNA is unzipping, one side is 5' to 3', the other is 3' to 5'. Since the polymerase can only extend off a 3' free end, one strand is being continuously replicated,

2008-10-02 09:57:29 補充：
while the other one will run into the previous Okazaki fragment and, at the same time, more DNA had been unzipped. So the polymerase need to hop off, move over to the newly unzipped DNA, and replicate that fragment again.

Is this clear?

大大您好
不論DNA或是RNA，合成的方向永遠是5'到3'
這一點就別問為什麼了，這是天降神旨阿....

是地，DNA複製時，其中一股可連續複製，另外一股為不連續複製。原因是負責DNA複製的DNA聚合酶III(以原核生物為例)為雙體(Dimer)。也就是說DNA聚合酶在進行複製時，是兩顆DNA聚合酶黏在一起坐在DNA雙股上(這樣說明大大您能想像嗎)。其中一股可以依循5'到3'的模式連續複製，但另外一股的方向就不行了...所以該股DNA就必須進行一種摺疊(Folding)，使的該股DNA一段一段慢慢做...

維基百科裡有圖說，會比較容易理解
http://en.wikipedia.org/wiki/DNA_replication

全是5"至3"!

2008-10-01 13:10:02 補充：
DNA複製時，"自已"的兩股都是5"至3"!
所以才會有岡崎片段!

2008-10-03 11:58:21 補充：
你的問題答案的理由盡在:5"至3"!
DNA的兩股方向是相反的!