Methyl changes:
If you have not seen “Lady and the Tramp”, do so before reading this.  It’s more fun and I would not like to be a spoiler.  The feature length cartoon by Disney is about two dogs, one pampered and the other a stray, who fall in love.  It contains my own personal favorite action scene of all time, the showdown between dog and rat in a nursery.  Among the characters, mostly dogs, there is an aged bloodhound, Trusty.  The climax of the show (spoiler alert, spoiler alert) is when in the midst of a seemingly impossible tracking operation Trusty catches the scent.

So we have an issue of vital importance and one day perhaps mainstream science will catch the scent.  Sometimes they come close.  (Not in the genes SCIENCE vol. 334 no. 6054 October 21, 2011 page  287 and Robert J. Schmitz et al Transgenerational Epigenetic Instability Is a Source of Novel Methylation Variants page 369 of the same issue) 

What they found was in the plant Arabidopsis, the methylation of DNA cytosine:
Diagram of a methyl group \,or.r_gc.r_pw.&fp=4e2387b06e8bc6cd&biw=1189&bih=452
Downloaded September 24, 2012. That’s the diagram of the base itself, the methylation is not shown. 

The methylation pattern changes orders of magnitude greater than genetic changes.  I think we knew that.  It has to be true if methylation differences are the cause of the infertility caused by insufficient consanguinity.  Then, the icing on the cake, while DNA mutations occur at random throughout the genome, these methylation changes occur in hot spots.  And these methylation changes are, to a degree, inherited and do cause differences in the phenotype of the organism. 

The fact that there are hot spots indicates that this variation has been selected for.  It confers some advantage.  Possibly it allows for varying phenotype in case the environment fluctuates.  I think one or more of those hot spots ought to be the source of the infertility that results from insufficient consanguinity.  It seems hard to imagine that the search is not on somewhere or other to find out just what each of the hot spots is up to.  The scent is in the track.  Hope that Trusty can find it.

There have been 68,190 visitors so far.

Home page