From “Preventing Dangerous Nonsense in Human Gene Expression” (ScienceDaily, Oct. 14, 2011), we learn:
Human genes are preferentially encoded by codons that are less likely to be mistranscribed (or “misread”) into a STOP codon. This finding by Brian Cusack and colleagues from the Max Planck Institute for Molecular Genetics in Berlin and the CNRS in Lyon and Paris is published in the open-access journal PLoS Genetics.
In biological systems, mistakes are made because the cellular machinery is complex and error prone. The errors made in copying DNA for transmission to offspring (genetic mutations) have so far been the primary focus of molecular evolution. But errors are much more frequent in the day-to-day task of gene expression, for example in the transcription of DNA into RNA. This study shows how human genes use a dual strategy of “prevention and cure” to deal with a specific type of gene expression error: transcriptional errors that create premature STOP codons (so-called “nonsense errors”).
Nonsense errors can be highly toxic for the cell, so natural selection has evolved a strategy called nonsense-mediated decay (NMD) to “cure” such errors. However, this cure is inefficient. This work identifies a strategy of prevention that has evolved to compensate for the inefficiency of NMD by decreasing the frequency of nonsense errors. Natural selection achieves this through the avoidance of codons that are prone to nonsense errors and the preferential usage of codons robust to such errors.
The authors offer no argument whatever that Darwin’s natural selection caused this correction mechanism; they merely assert it, expecting belief.
Follow UD News at Twitter!