DNA composed only of A and T?

[zephyr]

Hi, I have a very basic question about DNA.

Would it be possible to produce a double-stranded chain several hundred base pairs in length, composed almost entirely (90-95%) of A and T nucleotides?

Edited May 28, 2011 by zephyr

[insane_alien]

Yes it would be possible but almost entirely useless.

 

for one it would be extremely limited it the proteins it could encode as not every amino acid could be coded for.

[Fuzzwood]

Actually none at all, as you miss the "start here" codon which codes for methionine in our bodies.

[PrayingMantis.]

Indeed Fuzzwood got it! You need a start codon to begin with the translation (which is the process to turn the language of nucleotides to aminoacids). This start codon is AUG (copied from 3'->5' DNA with the sequence CAT to RNA). Of course you can make a DNA containing only A-Ts and it will have different propierties from a completely natural DNA, which is composed with C-Gs as well.

 

I hope this information can be handy for you.

[Greippi]

A large proportion of the human genome is composed of non-genomic (by that I mean not translated into protein/peptides) DNA (90% or something). Not all of it is translated. I am sure you'll probably find some nice islands of just A and T somewhere in there.

 

For example, regions of DNA rich in A and T are common in promoter regions.

 

However, the statistical likelihood of finding a several hundred basepair string of A and T is low.

 

Sorry if my response is burbled, I am very tired

Edited May 30, 2011 by Greippi

[CharonY]

Non-coding, not non-genomic .

Considering that the OP states that it just wants to create DNA with an artificial sequence, yes you can. DNA synthesizers can synthesize around 100 bp of DNA last time I looked (it could be longer by now) but you can use PCR to stitch them to longer sequences, if you wish. If they are to be translated you need at least a ribsome binding site and, as mentioned, a start-codon, both of which require G and C. However it would be achievable using the 90% limitation. If the question was whether the DNA is stable with a high AT content, then yes it is (there are repetitive sequences known consisting of long runs of simple repeats). While they have a lower melting temperature (and repeats make it hard for sequencing/assembly procedures), they are physically stable.