[Jinlim (OP)]

Hi, I have a question regarding the importance of the antiparallel nature of DNA in DNA replication.

I was wondering what would happen in DNA Replication if the DNA was NOT antiparallel in nature.

[chris]

The antiparallel (mirror-image) double-stranded nature of DNA makes it less error-prone because DNA replication machinery can cross-check the new sequence against the old one to see if it has introduced any errors.

But single-stranded nucleic acids - like the RNA molecules used by some viruses for example - are very prone to mutation when they are copied - because there is no complementary second strand to compare with, so unlike DNA, the RNA replication machinery has no inbuilt error-checking.

Indeed, the error rate for HIV is 1 in 10^4. In other words, the virus makes a mistake copying its genetic material every 10,000 genetic letters that it copies.

This is why common colds, the flu, and HIV change so rapidly.

It's not really possible for the DNA not to be antiparallel - unless you use single-stranded DNA of course - so there will always be error-checking when assembling the complementary strand and excision of incorrect (unmatching) bases.

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[Jinlim (OP)]

Hmm, i waasnt exactly asking about RNA......i was simply asking what are the effects during DNA REPLICATION if the two complementary strands were NOT antiparallel.

like what would be the effect..would there be weak H-bonds between bases......would the lagging strand not exist....i was hoping for answer something along those lines.

[chris]

As I said, if the 2 strands are not antiparallel (because an error has crept in altering a few bases here and there) then a proof-reading mechanism will edit out the errors and correct them.

There is no way to produce 2 DNA strands that are not anti-parallel - a enzyme uses the complementary sequence to assemble the opposite DNA strand.

You can artificially produce oligonucleotides which are not 100% complementary to the target you want them to bind to - for instance to engineer a restriction site - they just won't anneal so well...

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[Qing]

I don't know if it's correct, but i think it's not possible to get 2 strands parallel to each other because it is impossible to form hydrogen bonds between 2 same purines, or 2 same pyrimidines. imaging if you lay out the strands parallel to each other, one strand is going to be the mirror image of the other, so, they are going to repel each other.

Qing

[MayoFlyFarmer]

They don't repel eachother, but they won't form bonds strong enough to keep them together.  However, I still don't think this addresses the question that was asked.  Unfortuntely I still haven't been able to come up with one.  I don't really think there is an answer, because since so much of the cellular macheinary is designed around this concept, none of it would work.  You can't look for examples of it in nature, because you'd have to go back in evolutionary time to before the origins of life and completely start over....  who knows how nature would design things the second time around.

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