What is ..

[cellec]

What is Okizaki fragment ?
Does it have anything relating to biology ?
Thanks in advance,

[phreak]

I'm not a biologist (I'm more of a physicist), so I couldn't give you a good definition, so here's one from Wikipedia:

An Okazaki fragment is a relatively short fragment of DNA that is created by primase and Pol III along the lagging strand (see DNA replication). They are later removed by Pol I. The gaps remaining between the fragments are linked together by DNA ligase.

And yes, it appears to have something to do with biology.

[Monique]

DNA can only be elongated 5´ to 3´ directionally by DNA polymerase. Since you have two strand of DNA hybridized to each other into a helix, you have 4 ends total in the following configuration:

5'----------------------3'
3'----------------------5'

These two strands will seperate from eachother, while a part remains hybridized. A new strand can be synthesized on the single stranded part.

The following image http://nitro.biosci.arizona.edu/courses/EEB105/lectures/DNA_replication/zfigures/DNA_rep4.GIF shows you how on the leading strand 5'->3' synthesizes is possible, but on the lagging strand primers are needed = okazaki fragments.

[loseyourname]

Does this question have anything to do with me?

[cellec]

Does this question have anything to do with me?
Sure, your signature made me wonder. I thought it was a joke because it sounded like kind of a fruit's name than a biological term.
But why are you lagging ?
May I ask ?

Thanks

[cellec]

By the way, Thanks Monique and phreak for having answered my question...

[loseyourname]

But why are you lagging ?

When DNA is replicated, the 3'->5' strand is replicated slightly behind the 5'->3' strand, and so is referred to as the "lagging" strand.

As Monique said, DNA can only be synthesized in the 5'->3' direction. Because of this, the 5'->3' strand can be synthesized continuously, like this:


5' - 3'
5' - - 3'
5' - - - 3'
5' - - - - 3'

etc.

The 3'->5' strand, on the other hand, must be synthesized backward, like this:

3' - 5'
3' - - 5'
3' - - - - 5'
3' - - - - - 5'
3' - - - - - 5' 3' - 5'
3' - - - - - 5' 3' - - 5' {These fragments are referred to as "Okizaki" fragments
3' - - - - - 5' 3' - - - 5'
3' - - - - - - - - - - - 5'

[cellec]

Well, it takes you time to draw out that image...
Thanks loseyourname a lot for your explanation,