
Originally Posted by
Craig.Paardekooper
The Crispr database does not seem to include long sequences that repeat. I took the first Archea in their list, and found that it contains a sequence of 306 bases that repeat once.
GGGGTTATAGTAGGCCCTTCTCACATGCTCCTAGACATTTTTACAGAAAG AGGAATCTACCACAAGGTTAACGGAAGGTGGAGGAGAATAGCTTTAGCAC ACTTCTCTTATGATAACCCCATTGTCAACGGATTAGCAATAATAGCAGGA GTTATAATGCTGTTTGCAGCAATACATAATCACAACTATGATTACTACTA CCAATATTATCATTATTACAACTATTATTCCTAGTGAGATAATATACGAA AAGAGAAATATTTTTAAATACATTTTCTATATCTTTTGTCGTGATTTGTG AGAAGT - occurs at position 458021
GGGGTTATAGTAGGCCCTTCTCACATGCTCCTAGACATTTTTACAGAAAG AGGAATCTACCACAAGGTTAACGGAAGGTGGAGGAGAATAGCTTTAGCAC ACTTCTCTTATGATAACCCCATTGTCAACGGATTAGCAATAATAGCAGGA GTTATAATGCTGTTTGCAGCAATACATAATCACAACTATGATTACTACTA CCAATATTATCATTATTACAACTATTATTCCTAGTGAGATAATATACGAA AAGAGAAATATTTTTAAATACATTTTCTATATCTTTTGTCGTGATTTGTG AGAAGT - occurs at position 967546
THis is the longest repeat within the archaea - Acidianus hospitalis
I think duplicates like that might be a major force in evolution. If a whole gene accidentally gets duplicated, then the second gene is a free space to add/change code for a similar but different function than the first without disrupting the original functionality.
ETA: After writing that line I Googled "gene duplication" and found this wiki article:
Gene duplication is believed to play a major role in
evolution; this stance has been held by members of the scientific community for over 100 years.
[3] Susumu Ohno was one of the most famous developers of this theory in his classic book
Evolution by gene duplication (1970).
[4] Ohno argued that gene duplication is the most important evolutionary force since the emergence of the
universal common ancestor.
[5] Major
genome duplication events are not uncommon. It is believed that the entire
yeast genome underwent duplication about 100 million years ago.
[6] Plants are the most prolific genome duplicators. For example,
wheat is hexaploid (a kind of
polyploid), meaning that it has six copies of its genome.
The duplication of a gene results in an additional copy that is free from selective pressure. One kind of view is that this allows the new copy of the gene to mutate without deleterious consequence to the organism. This freedom from consequences allows for the mutation of novel genes that could potentially increase the fitness of the organism or code for a new function. An example of this is the apparent mutation of a duplicated digestive gene in a family of
ice fish into an antifreeze gene.
Another view is that both copies are equally free to accumulate degenerative mutations, so long as any defects are complemented by the other copy. This leads to a neutral "subfunctionalization" or DDC (duplication-degeneration-complementation) model,
[7][8] in which the functionality of the original gene is distributed among the two copies.
The two genes that exist after a gene duplication event are called
paralogs and usually code for
proteins with a similar function and/or structure. By contrast,
orthologous genes are ones which code for proteins with similar functions but exist in different species, and are created from a
speciation event. (See
Homology of sequences in genetics).
Makes a lot of sense to me.
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