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Posted by Hobart Carr on May 8, 2008, 7:55 pm, in reply to "Re: Is a clone as good as the original?"
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Excellent discussion here and thanks to Knabe you have my attention. Listen to his insightful and informed words.
Yes with every clone Mitochondrial DNA differences do exist. Many cow family success stories within breeds are directly attributable to their mitochondrial DNA. As the energy tranformer of the cell mitochondrial efficiency is key to unlocking the potential to the gentic code. How much influence mitochondrial DNA has ultimately on performance is difficult to measure but easy to identify. Good milking cow families that still are able to rebreed under stressful conditions demonstrate this effiency of utilizing their energy sources.
Chromosomal DNA expression is not just regulated by mitochondrial efficiency either. Many so called "Epigenetic" effects are controled by the Histone proteins that DNA is coiled around in storage. The epigenetic effects are influenced by a myriad of environmental factors that are not fully understood and are just now coming to light. These "Methylated" Histones target their regions of Chromosomal DNA for genetic expression or genetic silence. Perhaps the environment clones are raised in can affect the expression of their DNA. No, clones do not share mitochondrial, or chromosomal DNA with their recips, but the condition of the recip, as well as the environment she gestates, calves, and nurses her clone calf may turn out to have small but potentially significant effects on both Mitochondrial and Chromosomal DNA expression in offspring.
As far as an extremely small mutation rate dramatically affecting the phenotypic expression of clones I'm not buying that argument. If you had 1000 clones you would be hard pressed to find one spontaneous mutation that could be tied to a dramatic difference in tranmitted penotypic qualities. Over millions of years yes it will have an effect, but as far as Heatwave goes don't hold your breath that a TH negative spontaneous mutation will happen in your lifetime though cloning. Besides, then that animal would have no TH advantage.
Telomeric shortening and the negative effects on chromosomal DNA stability has been sighted as a complication in cloning, but in a way is itself an epigenetic phenomenon. Telomeres are chromosomal DNA that in essence protect the DNA that codes for proteins that form the biomass of the animal we ultimately consume. They reside at the ends of the chromosomes and act as the sheen, or glue that prevents chromosomal "split ends".
Bottom line. Yes there is potential for slight differences between clones. From my perspective I doubt that it is worth an exta 40 bucks if you are breeding a large # of cows, or an entire herd of club calf cows in mass.(with heatwave good luck getting some sleep).
However, if you are flushing a cow to produce further potential seed stock you can make the argument that the genuine article is the safest bet. With Heatwave I say this somewhat tongue in cheek because He already is a genetically "defective" Bull.
Defective enough to win just about every show, but also defective enough that his genetic merit cannot be multiplied through generations.
I theorize that the genetic merit of TH and PHA is likely the direct consequence of improved efficiency of gene expression. If there is only one functional copy of DNA expressing a key growth factor, protein, or substrate for cellular machinery then there is only one way that DNA can be unfolded and transcribed. If there are two effective genes that can be expressed then there will be a lag in efficiency with both potentially attempting to be expressed. Whith double heterozygosity as with the appropriately named Double Vision even further efficiency is attained and can explain these animals tremendous early maturity in muscle and bone expression.
Obviously they are one generation wonders. They are not commercially or economically viable in meat animal production in the long term.
BUT we should't confuse successful show cattle with commercially viable cattle. That difference has been present since the inception of showing cattle. Visual appriasal is by its nature arbitrary, capricous and based in no quantifiable human gain other than "aesthetics" or "image". I for one recognize, and embrace this reality just as I do both types of cattle.
Respectfully,
Hobart Carr
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