If it won't open for you, try addressing the IDEAS in the body of posted material:
hat the genetic code would have no variants was another failed prediction of Darwinism (like the prediction DNA would be filled with useless relics of evolution - junk DNA).
From the mid-1960s, when the code was discovered and explored, until about 1990, the prediction of a necessarily invariant, or universal, genetic code was widely held to follow from the theory of common descent. Almost any biology textbook from1966-1990 carries the prediction. Here are some of those predictions in writing:
Is the code necessarily invariant?
Functionally speaking this would appear to be a system that cannot vary. As Watson et al. (1987, 453) express the point, in their widely-used molecular genetics textbook:
Consider what might happen if a mutation changed the genetic code. Such a mutation might, for example, alter the sequence of the serine tRNA molecule of the class that corresponds to UCU, causing them to recognize UUU sequences instead. This would be a lethal mutationin haploid cells containing only one gene directing the production of tRNAser, for serine would not be inserted into many of its normal positions in proteins. Even if there were more than one gene...this type of mutation would still be lethal, since it would cause the simultaneous replacement of many phenylalanine residues by serine in cell proteins.Lehman (2001, R63) calls this functional gulf "a 'Death Valley' in the adaptive landscape." Retrospectively considering the prediction of universality, he writes,
The standard view of the evolution of the genetic code had been that, once the code became fixed in some primitive lineage of organisms, then any coding change would be precluded because the transitory coding stage that a population must experience to change its code would be lethal.Consider, for example, mutations that change the charging specificity of a tRNA aminoacyl synthetase, such that it charged a glycyl-tRNA with arginine instead. Suddenly glycines are replaced by arginines throughout the genome, which would undoubtedly cause irreparable cellular chaos. This could be thought of as the quintessential case of stabilizing selection: a 'Death Valley' in the adaptive landscape. (2001, R63; reference numbers omitted)Davis (1985, 256) provides a characteristic formulation of the prediction:
If organisms had arisen independently they could perfectly well have used different codes to connect the 64 trinucleotide codons to the 20 amino acids; but if they arose by common descent any alteration of the code would be lethal, because it would change too many proteins at once. Hence the finding of the same genetic code in microbes, plants and animals...spectacularly confirms a strong evolutionary prediction.Students and teachers should know about these predictions, which (as noted) were widespread in the biological literature for nearly three decades. Understanding how predictions from evolutionary theory may fail, or be modified, is an important aspect of biological knowledge. What students and teachers should not be told is "well, we knew that all along -- no surprise here." Such a response passes beyond historical revisionism into outright falsehood.
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