Kornberg showed that nucleotides are added to the 3' end of each growing DNA strand. In what way does an exposed 3'-OH group participate in strand elongation?

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Hi everyone here's our next problem. It says DNA polymerase three adds nucleotides to a primer to synthesize the new strand of DNA in order to link the nucleotides. A phosphate ester linkages established between. Well let's recall that our DNA when it synthesizes, always synthesized in the direction five Prime 3 prime. And we add on nucleotides onto a growing new strand. Um That's that's matched up with a template strand so we can go ahead and limit two of our answer choices because two of them involve the nucleotide being added onto the template strand. Um But that's not correct. The template strand is there? The nucleotide is added on to the growing strand that's paired to the template strand. So A. And B. Are going to be incorrect because they have the template strand in there. So now let's look at C. And D. He says the three prime O. H. Of the already paired strands and the five prime O. H. On the phosphate of the incoming nucleotide choice. D. Says the five prime O. H. The other way around on the already paired strand, the three prime O. H. On the incoming nucleotide. But again we know our DNA. Has to be synthesized in the five prime 23 prime direction. So the new nuclear tide must be linked onto the three prime end of that already paired strand. So that's going to be in our choice C. Three prime away to the rd paired strand being linked to the five prime. Oh wait on the incoming nucleotide. So choice C. Is gonna be our answer here choice D. Is incorrect because it hasn't in the reverse order. It has the three prime O. H. On the sugar of the incoming nucleotide binding. The five prime O. H. On the already paired strand. But that would be in the wrong direction. So that's why D. Is incorrect. So I'll just put up a quick diagram here so we can see a more detailed look at exactly what's going on. So at the top here this is our last nucleotide in the already paired strand. So the three prime end we see the the other nuclear tied. The rest of nucleotide would be going on up here. Here's the three carbon three in that nucleotide and it has this phosphate group. Um With an O. H. Here. Then here's our incoming nucleotide. And we see on carbon five here oops that on carbon five we have an O. H. Here our fossil diaspora bond is going to form by the elimination of a water molecule. And then the phosphor diaspora bond that forms we'll be here. So that will add on our incoming nucleotide onto the three prime end of are already paired strand. See you in the next video

Kornberg showed that nucleotides are added to the 3' end of each growing DNA strand. In what way does an exposed 3'-OH group participate in strand elongation?

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Key Concepts

DNA Strand Elongation Directionality

Role of the 3'-OH Group in DNA Polymerization

Function of DNA Polymerase in Strand Elongation