Scientists at the University of Illinois have discovered an antifreeze-protein gene in cod that has evolved from non-coding or ‘junk’ DNA.
“This appears to be a new mechanism for the evolution of a gene from non-coding DNA”, says Professor Cheng, “3.5 billion years of evolution of life has produced many coding genes and conventional thinking assumes that new genes must come from pre-existing ones because the probability of a random stretch of DNA somehow becoming a functional gene is very low if not nil. This cod antifreeze gene might be an exception to this because it consists of a short repetitive sequence that only needs to be duplicated four times to give a fully functioning protein”.
This antifreeze gene and the Drosophila Acp’s I mentioned previously have one thing in common: they encode short proteins. This brief report does not specify how short the repetitive sequence is, but Acp’s are less than 50 amino acids (150 nucleotides) long. Research into their origins may shed light on the evolution of the first protein coding genes.