Our ancestors originally had 24 pairs of chromosomes, the last with 700 genes each until they shed enough to combine with the 23rd pair, forming our modern sex chromosomes. The new X stabilized at 1,100 genes, but Y continued to shrink and now has a mere 27 genes. While any absent/damaged X genes in one parent can be filled in with the other parent's good copy, males inherit their father's Y chromosome directly, and any mistakes in transcription are thus passed on to the next generation.
The popular theory is that Y will keep shrinking until it combines with another chromosome, which will then take over its task. A much more optimistic theory has come out of UC Berkeley:
The human Y, however, may be done shrinking, says Wilson Sayres...the lead author of a new analysis that suggests the Y isn't shrinking, it's honed. It has one job and one job only. ...
"The few genes that are left on the Y, if you lose them, you have big problems ... Sperm don't swim, their heads are malformed, they can't fertilize an egg."
Sayres feels this explains why Y chromosomes around the world have only 1/10 of the genetic variation other chromosomes do. The old "Genghis Khan" theory was that a few men produced far more offspring than others did, but a complex computer DNA simulation proved that there's too much variation in the human genome for it to work. In other words, we're the product of only the best Y-chromosome genes on a huge variety of men not primarily the historic aggressors nature might consider the 'best' at reproducing.
(Score: 0) by Anonymous Coward on Monday April 21 2014, @12:17PM
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(Score: 1) by VortexCortex on Monday April 21 2014, @03:26PM
Not only is the Y chromosome optimized for efficiency, its lesser ability to correct errors may help introduce genetic diversity so that selection pressure can converge on advances more quickly.
In my simulations of breeding artificial cybernetic beings I find the "sweet spot" of desired error introduction rate changes over time, depending on the fragility of the feature set emerging. For a complex adaptation to persist it must become prevalent rather quickly, or it will be lost to entropic forces. Too much error correction can prevent even advantageous adaptations from occurring by erasing the adaptation in subsequent generations. The same high entropy environment that produces more complex advantages is also more likely to erase them. Advantages share the same crap shoot that is a being's own existence; There's no guarantee that a beneficial adaptation will survive, just that the being with one is more likely to do so. Nature's ultimate law is: Adapt or become Extinct. Those creatures with more perfect replication adapt more slowly. The dangers of genetic defects are the price we paid for our ability to adapt more quickly and fend off extinction better than our competitors.
Currently my sims use an artificial genome which have effects tied to sections of the genome algorithmically. Eventually some genetic simulations will operate via actual DNA emulation and will be able to accurately model any variety of living being based on their DNA. This will find use not only in Forensics. [nature.com] The livestock industry will immediately utilize the tech for designer stock. Gene therapy is already using retroviruses to correct genetic problems. Notably, you don't see as many "Bubble Boys" because we can fix their immune systems and histamine responses if we catch the problem early enough. More accurate gene sims will allow us to diagnose and develop treatments for a wider array of genetic diseases. It is widely considered unethical to experiment on human DNA and potentially cause live human offspring horrible mutations; However, if we can see the change our modifications produce in a simulated environment then we will be able to avoid many of the ethical issues of human genome experimentation; Gene sim will also greatly reduce the burden of animal testing.
Instead of having to fine tune the genetic error rates manually, in my sim environments there are varying intensities of "cosmic rays" or "radioactive elements" -- a gradient of error introduction tied to position in the sim via Perlin noise function, as gradual changing global variable, or other combinations or more complex scenarios (radioactive beings or foods/energy sources [super bananas], etc.) This allows more complex features to emerge if they require multiple simultaneous mutations (more errors), while also allowing the adaptation to spread to less entropic regions and become dominant via speciation. Just like life is more likely to emerge at an energy gradient such as a thermal sea vent or planet's atmosphere, the varied intensity of cosmic rays between deep water, shallow water, and land may help accelerate emergence of complex features too -- an entropy gradient instead of an energy gradient.
When selection is allowed to operate on error correction capabilities of genomes themselves I have seen similar results whereby the genome itself will adapt to take advantage of selection pressures directly. My simulated genomes can become more protected in some sections where mutations are frequently fatal and less protected in other sections where mutations are less fatal and diversity is advantageous; Much the same as the human X and Y chromosomes appear to be. As we take more command of this planet's genomes we may also be able to control mutation rate itself by applying more rigorous corrective systems to vital areas of a genome while relaxing the correction rate in other mutation friendly or merely aesthetically linked sections.
In short: There are advantages to having different error rates even within a single genome.
(Score: 2) by fishybell on Monday April 21 2014, @03:44PM
As long as I also get to un-fur myself permanently I'm okay with that. Right now, every day, more hair, more places. I will soon be a gorilla, and no one wants that (except the furries).
(Score: 1) by NickM on Monday April 21 2014, @07:34PM
I a master of typographic, grammatical and miscellaneous errors !
(Score: 1) by NickM on Monday April 21 2014, @07:37PM
I a master of typographic, grammatical and miscellaneous errors !
(Score: 2) by Rivenaleem on Tuesday April 22 2014, @12:31PM
By the samples you have not seen?
(Score: 1) by NickM on Tuesday April 22 2014, @09:36PM
I a master of typographic, grammatical and miscellaneous errors !
(Score: 1) by Hawkwind on Monday April 21 2014, @10:30PM
Thanks for the write-up, hopefully the mods will eventually see this. And good luck!
(Score: 0) by Anonymous Coward on Monday April 21 2014, @07:28PM
Wow! Men really do travel lighter than women!
(Score: 2) by Rivenaleem on Tuesday April 22 2014, @12:35PM
Y Chromosomes give Slack Genes the Boot.