The DNA code is made up of codons (3-letter words) derived from 64 different arrangements of bases linking the two DNA strands. Yet these 64 combinations code for only 20 amino acids and a stop signal. Thus, different codons are able to produce the same amino acid. The phenomenon is described as the genetic code having “redundancy”. In the early years of molecular biology, this redundancy was perceived as an evolutionary accident, unworthy of detailed research but fortunate because it meant that any damaging effects of point mutations were cushioned. However, the evidence has been accumulating that “redundancy” is a misleading word.
“Scientists have known about this redundancy for 50 years, but in recent years, as more and more genomes from creatures as diverse as domestic dogs to wild rice have been decoded, scientists have come to appreciate that not all redundant codons are equal. Many organisms have a clear preference for one type of codon over another, even though the end result is the same. This begged the question the new research answered: if redundant codons do the same thing, why would nature prefer one to the other?” (Source here)
New research into protein synthesis in bacteria has shone new light on these issues. “A hidden and never before recognized layer of information in the genetic code has been uncovered by a team of scientists” using a technique called ribosome profiling. This tool allows gene activity inside living cells to be monitored, including the speed with which proteins are made.
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