about DNA ?

[1123581321]

I was wondering, if you impregnated an organism with foreign genes - that is genes which are not known or recognized by that organism (its genome). Would the developed embryo (later on) contain DNA with no function within its genome, in other words 'junk DNA'. And would this be true due to the foreign DNA literally having no role to play within the organism for which it has no (natural) function...

[dttom]

To have what you said done, the piece of foreign DNA should be integrated into genome (how to get in cell? how to be integrated?), the chances are very low especially without homologous sequence for homologous recombination; even if it comes in, it will mostly be a mosaic instead of a genuine organism with all genomes identical.

Edited November 2, 2010 by dttom

[DctrZaius]

There isn't really such a thing as "genes which are not known or recognized by that organism". If you transfect an organism with any gene, the cellular machinery will express the gene. All DNA is made up of the same four nucleotides so the RNA polymerase of an organism doesn't 'know' if the sequences within the genome are 'natural' to that organism; it can't tell if there's something introduced and will therefore express any gene it can bind to. The only time the organism won't express the gene is if there is no promoter upstream and RNA Pol can't bind to that sequence. You can transfect an organism with DNA that doesn't code for any functional product, however (with regard to your interest in the DNA playing no role).

[CharonY]

Well, for any gene to be expressed you require the cis-regulatory elements. If you leave them out, they won't be transcribed. Viruses could insert inactive sequences (or become inactive later due to mutations), which happned quite frequently in the human genome. However, just not being expressed does not mean that during evolution it may not gain some kind of function. It can, for in stance, modulate the DNA structure and thereby influence expression of other functional genes.

[CylonHybrid]

Um, the answer is they wouldn't be expressed because of a new new way in which the cell regulates itself known as RNAi. The inserted gene would be silenced as was observed in the 1980s when attempts to insert a transgene on a vector to flowering plants resulted in silencing of both the inserted gene and the endogenous gene.

Its a defense mechanism against both retroviruses and normal DNA viruses which attmept to insert their foreign genome into the genome of the plant so that the viral genome can replicate and produce more of themselves during the lysogenic phase.

Either through post transcriptional or transcriptional silencing the gene is not expressed.

 

 

And dttom, you can still use a p element to recombine the transgene using non homologous recombination, its just that the frequency of recombination would be very low.