Can I get some help with homework please? DNA replication

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lolPirate
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Can I get some help with homework please? DNA replication

Post by lolPirate » Mon Dec 07, 2009 9:32 pm

I have this page for biology and I don't know what to put for number 3 and help would be appreciated :D . Also do the rest of my answers look right?

http://img694.imageshack.us/i/dnareplicationcopy.jpg/

1.) this process being at a site (where the X's are) on the DNA called:
origin of replication

2.)What are the names of molecules 1 and 2?
topoisomerase and single stranded dna binding proteins

3.)What kind of molecule is #4 made of? Name the exact monomer used.
This one I do not know.

kolean
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Post by kolean » Tue Dec 08, 2009 1:52 am

From the photo, to me it looks like the RNA primer that is used to initiate the Okazaki fragment on the lagging strand. The monomer of the RNA primer is a ribonucleotide (RNA), and not a deoxyribonucleotide (DNA).

Your other answers look spot on. I wonder why you said topoisomerase instead of helicase?

lolPirate
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Post by lolPirate » Tue Dec 08, 2009 5:20 pm

Well I had helicase at first but on all of the pictures I looked at the hilcase was inside of the "bubble" and the topoismerase was on the outside. Are they the same thing or something? I suck at bio haha

kolean
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Post by kolean » Wed Dec 09, 2009 4:56 am

Topoisomerase cuts one strand, flips it, and then anneals it back together, in order to keep the DNA from becoming supercoiled when the strands are being pulled apart:
http://en.wikipedia.org/wiki/Topoisomerase
While on the other hand Helicase is the one that is in charge of actually separating the two strands (interupts the hydrogen bonding going on between the complementary bases):
http://en.wikipedia.org/wiki/Helicase
So it makes sense that the helicase would be inside the bubble, or at the begining of the strand separation, while the topoisomerase would be first to nick the DNA so the double helical strands could be tension free to begin to be separated.

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