Genetic Diversity Where None Was Expected

Most scientists had believed until recently that silent mutations had no effect on an organism. Thanks to researchers at the Univesity of Pennsylvania, we have learned that "silent mutations" -- although they do not change the encoded protein product of the gene -- can change the quantity of the encoded protein that is produced.

The silent mutations changed the amount of fluorescent protein by as much as 250-fold, without changing the properties of the protein. Codon bias, the probability that one codon of three adjacent nucleotides will code for one amino acid over another, was previously thought to be the cause for protein expression variance, but it did not correlate with gene expression in these experiments.

"At first we were stumped," Plotkin said. "How were the silent mutations influencing protein levels? Eventually, we looked at mRNA structure and discovered that this was the underlying mechanism." MedNewsToday

The number of ways that humans can vary by gene expression, yet still possess almost identical genomes on superficial inspection, is immense and growing larger.

Non-coding RNAs are a large part of the reason why. "Junk DNA" that isn't really junk. The surface of gene expression and gene switching is barely being scratched, and now we find yet another source of subtle variation in gene expression.

These are exciting times for geneticists and for anyone with an interest in gene expression, and potential gene therapies.