Dna............?

what is the "code" for DNA that assures that an exact coppy is made?Dna............?
It doesn't sound like you mean the triplet code. I think what you mean is that A can only pair with T, and C with G.Dna............?
what do u mean?

the genetic code?

or that DNA is made of complementary base pairings so that only the base Adenine can bind to Thymine

and only Guanine can bind to Cytosine. This enures that an exact copy is produced.Dna............?
the short answer is semiconservative replication.



the long answer is as follows...



DNA is a two stranded molecule, think of it the two sides of a zipper (this is not so far off)



DNA has four major componenets in its "code" and these four componenets are called "nucleotides". There are 4 different nucleotides, Adenine, Guanine, Cytosine, and Thymine, but people just abreviate these to A, G, C and T to make it easier.



Now think of DNA as a long string made up of these nucleotides linked together one after another, so you could have...



....AAAGTCA....



or whatever you want.



Now remember we said that there were two strands like that. The second strand has to match the first one very specifically. They line up side by side, and the nucleotides match up. What I mean by this is that A always has to match with T, and C always matches with G.



To simplify, if one strand of DNA is...



...AAAGTCA...



then the second one has to be...



...TTTCAGT...



Now when DNA is going to copy itself, the two strands split up and then new nucleotides are added to each individual DNA strand to "match". Since each nucleotide can only pair with a specific other nucleotide, the only copy that can be made is an exact copy.



So in the end after copying the 2 stranded DNA molecule to get 2 new DNA molecules, the two new molecules each have one strand of DNA from the original copy (this one was like a blueprint for the second) and a second copy which was built new.



hope that makes sense!
Naturally, the base pairs are specific (A-T, G-C).



The enzyme that places nucleotides in sequence, DNA Synthase, does a self check and corrects any mistakes as it goes along, and Ligase does some help too.



The system is pretty nifty!