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Can a gene be situated at multiple loci in a genome?

Genetics as it applies to evolution, molecular biology, and medical aspects.

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Can a gene be situated at multiple loci in a genome?

Postby ruefi » Tue Nov 03, 2009 1:14 am

Does it happen that one sequence of a given gene is repeated multiple times at multiple loci in a chromosome?
I would imagine that this way, more mRNA and therefore more protein could be produced per time unit in a kind of "parallel production". This might be useful for producing proteins that are needed in large copy numbers in a cell. But I have never heard of this before and for all genes I have seen so far a single locus was given.
Thanks a lot,
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Postby TheVirus » Tue Nov 03, 2009 2:07 am

Maybe it's not what you mean, but (and i'm not sure about it) i think it is possible for a gene to be repeated in the telomeres, which are disposable dna "plugs" at the end of the chromosomes. See, after each replication, a portion of dna material is lost from each chromosome. Telomeres act like some kind of "kamikazee" part of the chromosome which is got rid of after each replication instead of the actual genetic code and since this are just random sequences of dna (i think) maybe it's possible for a gene to be repeated there (long shot).
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Re: Can a gene be situated at multiple loci in a genome?

Postby JackBean » Tue Nov 03, 2009 7:20 am

Yes, there are such genes, like for rRNA are many copies in tandem (e.g. in human about 200 copies, in Xenopus even 600 copies) and also for histones, I think.

But also, there are sometimes genes duplicated by chromosome rearragnment. In that case, whole part of chromosome can be duplicated and connected to another chromosome, that's for example the case of maize, which has huge genome and many genes has duplicated in this way :wink:
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.
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Postby Darby » Tue Nov 03, 2009 3:31 pm

The repeats in telomeres are not genes - they don't code for anything.

Duplicate genes can come from several different types of mutations, but just because you have extra copies doesn't mean you express all of the equally, or at all.

And in some cases extra copies are the basis for brand-new genes, which can mutate to new functions without disturbing the functions supported by the "original" genes.
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Postby TheVirus » Wed Nov 04, 2009 2:21 am

Cool...and if there are multiple copies of the same gene, would that affect at all how the protein or RNA molecule the gene codes for is produced in the cell?
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