lagging strand

[joonkimdds]

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I am learning about DNA now, and I didn't understand what lagging strand is.
both leading and lagging strands are daughter strand of DNA during DNA replication.

In my textbook, it says leading strand is 5' => 3', and lagging strand is 3' =>5'. but the picture i see shows that lagging strand is 5'=>3'.

so, i went to google website and found its definition. it says

Lagging strand
"In DNA replication, the strand that is synthesized apparently in the 3' to 5' direction, but actually in the 5' to 3' direction by ligating short fragments synthesized individually. Strand of DNA being replicated discontinuously. See also leading strand."

I don't understand this. it says 3 to 5 but actually it's 5 to 3.
which one is the truth?

 

[howui3]

recall that ALL dna replication occurs 5 prime to 3 prime.

One of the stands will be replicated into the replication fork so that as the DNA unwinds this strand can continue to replicate without interruptions - that is the leading strand.

The lagging strand will create Okazaki fragments becuse it will be replicated in the other direction.

check out your bio textbook.

good luck.

 

[joonkimdds]

recall that ALL dna replication occurs 5 prime to 3 prime.

One of the stands will be replicated into the replication fork so that as the DNA unwinds this strand can continue to replicate without interruptions - that is the leading strand.

The lagging strand will create Okazaki fragments becuse it will be replicated in the other direction.

check out your bio textbook.

good luck.

I chekced out my bio textbook. It says DNA replication occurs 5' to 3'.
it also says daughter strand that occurs 5' to 3' direction is leading strand and the daughter strand that goes to the opposite direction lagging strand.

When I look at the picture, it shows those 2 strand with arrows. When I look at the arrow, even the lagging strand points from 5' to 3'.
I compared the definition with that arrow and that's when I started to become curious.

When I saw the definition from the internet, it says lagging strand is 3' to 5' but actually it's 5' to 3'. This definition confused me again.

The definition and the picture from the bio textbook were different, and the definition from the internet says both.


Here is one of the picture that is similar to what I saw from my text book.
http://cwx.prenhall.com/horton/medialib/media_portfolio/text_images/FG20_09.JPG


If u look at that picture, both leading and lagging are 5' to 3'.

Now, How should I distinguish leading and lagging if both of them are from 5' to 3'?

 

[tinman831]

If you look at the double strand of DNA, you see one strand is in the 5' to 3' direction and the other strand is in the 3' to 5' direction.

The polymerase can only read the original strands of dna in the 3' to 5' direction. If you look in your picture, imagine that the polymerase traveling down the parental strands from the right to the left in your picture. The polymerase will read the top strand just fine (because its 3' to 5'). That means the polymerase will go straight down the top strand from left to right and form a complete daughter strand.

Now keep in mind the fact that the parental strand needs to be read in the 3' to 5' direction. How does the polymerase read the bottom strand since the bottom strand is going the opposite direction as the top strand? What the polymerase does is it jumps ahead a little bit, and then reads the bottom backwards. Then the polymerase moves to the left a bit more, and reads it backwards. This creates a bunch of small fragments.

The leading strand is the parental strand (the top strand in your picture) that makes one continuous daughter strand . The lagging strand is the strand of dna (bottom in your picture) that is not read continuously and produces okazaki fragments.

Did that make any sense?

 

[joonkimdds]

If you look at the double strand of DNA, you see one strand is in the 5' to 3' direction and the other strand is in the 3' to 5' direction.

The polymerase can only read the original strands of dna in the 3' to 5' direction. If you look in your picture, imagine that the polymerase traveling down the parental strands from the right to the left in your picture. The polymerase will read the top strand just fine (because its 3' to 5'). That means the polymerase will go straight down the top strand from left to right and form a complete daughter strand.

Now keep in mind the fact that the parental strand needs to be read in the 3' to 5' direction. How does the polymerase read the bottom strand since the bottom strand is going the opposite direction as the top strand? What the polymerase does is it jumps ahead a little bit, and then reads the bottom backwards. Then the polymerase moves to the left a bit more, and reads it backwards. This creates a bunch of small fragments.

The leading strand is the parental strand (the top strand in your picture) that makes one continuous daughter strand . The lagging strand is the strand of dna (bottom in your picture) that is not read continuously and produces okazaki fragments.

leading and lagging strands are parental strands?
I thought they were daughter strands.
The linked image also says the outer strands are parental and the inner strands(gray in the image) are leading and lagging.

And also, my bio textbook says DNA polymerase elongates DNA strands only in the 5'->3' direction, but you said it's from 3' to 5'.

 

[tinman831]

leading and lagging strands are parental strands?
I thought they were daughter strands.
The linked image also says the outer strands are parental and the inner strands(gray in the image) are leading and lagging.

I have two books with me that tell me two different things. I'd go with what your book says. Sorry about that.

And also, my bio textbook says DNA polymerase elongates DNA strands only in the 5'->3' direction, but you said it's from 3' to 5'.

I said that the template strands are read in 3' to 5'. The daughter strands do elongate in the 5' to 3'.

 

[BallDontLie]

I don't understand this. it says 3 to 5 but actually it's 5 to 3.
which one is the truth?

DNA is ALWAYS synthesized 5' to 3'...to actually understand it and not just memorize facts, just think about the chemistry. You need to have the free 3'-OH in order to add additional bases.

 

[joonkimdds]

DNA is ALWAYS synthesized 5' to 3'...to actually understand it and not just memorize facts, just think about the chemistry. You need to have the free 3'-OH in order to add additional bases.

yeah, i understand that DNA is always synthesized 5' to 3', but lagging strand definition says it is 3' to 5'.
If both leading and lagging strands move from 5' to 3' then what u said and what we see from the arrow in image http://cwx.prenhall.com/horton/medialib/media_portfolio/text_images/FG20_09.JPG make sense, but how would you redefine lagging strand and distinguish it from leading strands(without using okazaki fragments)?

 

[BallDontLie]

yeah, i understand that DNA is always synthesized 5' to 3', but lagging strand definition says it is 3' to 5'.
If both leading and lagging strands move from 5' to 3' then what u said and what we see from the arrow in image http://cwx.prenhall.com/horton/medialib/media_portfolio/text_images/FG20_09.JPG make sense, but how would you redefine lagging strand and distinguish it from leading strands(without using okazaki fragments)?

Not really sure what youre asking me here, cuz the two strands are distinguished by the fact that the leading strand is sythesized continuously and the lagging strand is made discontinously(hence the okazaki fragments).

 

[SuperC]

yeah, i understand that DNA is always synthesized 5' to 3', but lagging strand definition says it is 3' to 5'.
If both leading and lagging strands move from 5' to 3' then what u said and what we see from the arrow in image http://cwx.prenhall.com/horton/medialib/media_portfolio/text_images/FG20_09.JPG make sense, but how would you redefine lagging strand and distinguish it from leading strands(without using okazaki fragments)?

The difference between the leading and lagging strands are....
The leading strand is CONTINIOUS
The lagging strand is DIScontinious

Now... where you are (most likely) having trouble... Because both strands are anti-parallel, how can both strands be made in 5' -> 3'?

You really need to find a "real" replication animation. With out a drawing or an animation I think trying to expain how it "really" works will just confuse you. Pages 4 and 5 of this link may be help to you (from my genetics class last semseter) http://www.zoology.ufl.edu/genetics/images/Notes/10_06_05.pdf

Otherwise... For the DAT. All you will need to know is what direction is DNA replication and the functions of the pols. (which have exonuclease activity)

-C

 

[joonkimdds]

The difference between the leading and lagging strands are....
The leading strand is CONTINIOUS
The lagging strand is DIScontinious

Now... where you are (most likely) having trouble... Because both strands are anti-parallel, how can both strands be made in 5' -> 3'?

You really need to find a "real" replication animation. With out a drawing or an animation I think trying to expain how it "really" works will just confuse you. Pages 4 and 5 of this link may be help to you (from my genetics class last semseter) http://www.zoology.ufl.edu/genetics/images/Notes/10_06_05.pdf

Otherwise... For the DAT. All you will need to know is what direction is DNA replication and the functions of the pols. (which have exonuclease activity)

-C

Thank you Thank you Thank you.
even though ur note wasn't really that helpful, ur suggestion about animation really helped. 😍
http://www.ncc.gmu.edu/dna/repanim.htm was the link that i used to see the DNA replication animation.
Finally I understand it.

By the way, what's the functions of the pols? and what's pols ?

 

[Dr. Konfetka]

By the way, what's the functions of the pols? and what's pols ?[/QUOTE]


Not sure exactly what your asking, but POL is a shorthand way of wring polymerase.

 

[joonkimdds]

By the way, what's the functions of the pols? and what's pols ?

Not sure exactly what your asking, but POL is a shorthand way of wring polymerase.[/QUOTE]

he told me that i need to know the function of POL(polymerase) for DAT, so I was asking what are the functions of POL. I know something like DNA polymerase is an enzyme that catalyze the DNA replication or something like that but that's all i know, so if someone knows more than what i know, I hope you could teach me.

 

[SuperC]

Here is a really good animation that shows how both strands are replicated.
http://bcs.whfreeman.com/iga8e/pages/bcs-main.asp?v=chapter&s=07000&n=00020&i=07020.02&o=|00510|00520|00540|00530|00560|00570|00PRS|00010|00020|00030|00090|00050|01000|02000|03000|04000|05000|06000|07000|08000|09000|10000|11000|12000|13000|14000|15000|16000|17000|18000|19000|20000|21000|99000|&ns=0

As for the function of the polyemerases check out page four on this link.
http://www.zoology.ufl.edu/genetics/images/Exams 2005/Ex2_Solns.pdf