lagging strand okazaki fragment

[Roosevelt32]

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hey guys I'm studying a bit of bio but have trouble understanding the DNA replication process of Lagging strand/Okazaki fragement. Does the new strand of dna form? I'm confused grasping the lagging strand part.

 

[zEkii]

The lagging strand is literally "lagging" behind the Leading DNA strand. Because DNA Polymerase attaches and reads the DNA leading strand from 3' to 5'. But keep in mind that the Leading DNA will be synthesized 5' to 3'!!

Since, you know that now... We want the lagging strand to do the exact same thing as the leading strand. The only problem is, is that it is doing everything backwards. In order to fix that problem, we must use the RNA Primers to read it in "small fragments" and let the DNA POLY synthesize it a piece at a time. As we know it, this is called "Okazaki Fragments". It is lagging because of the extra process it needs to be able to follow the Leading Strands conformation.

Then a DNA Ligase attaches the Okazaki Fragments together and makes it consistent again! Hope that cleared up any confusion or atleast understand the concept

 

[BeaverLover]

DNA polymerase is only able to read in the 3'->5' direction, thus synthesizing a complement 5'->3' strand off of the template and needs RNA primers to be added only once at the beginning of the leading strand to synthesize a continous, complement strand. The problem with Okazaki fragments (lagging strand) is that DNA polymerase 3 can only read 3'->5' as previously mentioned but we're left with a strand going 5'->3'. So, the solution to this problem is to add multiple RNA primers in which DNA polymerase 3 can attach onto the primers and synthesize the molecule in pieces compared to the leading strand. DNA polymerase removes the RNA primers later on, and ligase connects the pieces together.

Google images okazaki fragment and try to imagine a continuous elongation & separation of the two strands by helicase. One strand reads 3'->5' and polymerase is capable of continuous replication with the addition of only one group of primers. This viewpoint can't be applied to the other (lagging) strand because it lacks a 3'->5' read, therefore multiple primers are necessary to read in the 3'->5' direction and replication occurs in small fragments and in opposite direction of the leading strand. Side note: primers add a free 3' hydroxyl group...i think thats what i remember correctly...

Not sure what RNA poly has to do with this, I think person got confused

 

[zEkii]

DNA polymerase is only able to read in the 3'->5' direction, thus synthesizing a complement 5'->3' strand off of the template and needs RNA primers to be added only once at the beginning of the leading strand to synthesize a continous, complement strand. The problem with Okazaki fragments (lagging strand) is that DNA polymerase 3 can only read 3'->5' as previously mentioned but we're left with a strand going 5'->3'. So, the solution to this problem is to add multiple RNA primers in which DNA polymerase 3 can attach onto the primers and synthesize the molecule in pieces compared to the leading strand. DNA polymerase removes the RNA primers later on, and ligase connects the pieces together.

Google images okazaki fragment and try to imagine a continuous elongation & separation of the two strands by helicase. One strand reads 3'->5' and polymerase is capable of continuous replication with the addition of only one group of primers. This viewpoint can't be applied to the other (lagging) strand because it lacks a 3'->5' read, therefore multiple primers are necessary to read in the 3'->5' direction and replication occurs in small fragments and in opposite direction of the leading strand. Side note: primers add a free 3' hydroxyl group...i think thats what i remember correctly...

Not sure what RNA poly has to do with this, I think person got confused

I jumped the gun here. I meant to say RNA primers for the lagging strand.

 

[510586]

The lagging strand is literally "lagging" behind the Leading DNA strand. Because DNA Polymerase attaches and reads the DNA leading strand from 3' to 5'. But keep in mind that the Leading DNA will be synthesized 5' to 3'!!

Since, you know that now... We want the lagging strand to do the exact same thing as the leading strand. The only problem is, is that it is doing everything backwards. In order to fix that problem, we must use the RNA Primers to read it in "small fragments" and let the DNA POLY synthesize it a piece at a time. As we know it, this is called "Okazaki Fragments". It is lagging because of the extra process it needs to be able to follow the Leading Strands conformation.

Then a DNA Ligase attaches the Okazaki Fragments together and makes it consistent again! Hope that cleared up any confusion or atleast understand the concept

Don't polymerase always synthesize in the 3 to 5 direction making a 5-3 strand? Just in opposite directions?

 

[adamrose]

Don't polymerase always synthesize in the 3 to 5 direction making a 5-3 strand? Just in opposite directions?

5'-----------------------------3' (original strand)
<------------ Direction in which DNA poly moves (3'->5')
l l l l l l l l (DNA polymerase makes the strand below)
<<3'-----------5' (new strand)

ok enough art back to studying

 

[DAT Destroyer]

hey guys I'm studying a bit of bio but have trouble understanding the DNA replication process of Lagging strand/Okazaki fragement. Does the new strand of dna form? I'm confused grasping the lagging strand part.

DNA polymerase is an enzyme, which means it will bind a substrate in a certain orientation.

It turns out, this enzyme only knows how to add new nucleotides to the growing strand to the 3' carbon of the sugar (ribose). So, the new strand starts from the 5' carbon, but added and growing at the 3' carbon, that is the only way polymerase is able to add to the growing chain.

Furthermore, since DNA is double stranded, same polymerase has to replicate both strands. It does so at the same time and only 5'-3' direction.
How?

Well, the strands are anti-parallel, so the enzyme will continuously synthesize one strand (leading strand 5'-3' direction), while the reverse and complimentary strand, must be synthesized in fragments while lagging behind. That is the only way to ensure 5'-3' synthesis on both strands.

There are some youtube videos to reinforce this concept.


Hope this helps

 

[Roosevelt32]

thanks everyone I understand now