A mutant strain of chickens with the ability to grow teeth during development has bolstered the evidence that traits lost during the evolutionary process remain hidden within DNA and can sometimes be coaxed out of dormancy.
UW-Madison researchers Matthew Harris and John Fallon found small alligator-like teeth when studying the development of a strain of chickens, according to a report in The Milwaukee Journal Sentinel. The discovery brings to light the subject of throwbacks,\ genetic signals and traits coming back after up to millions of years without activity. UW-Madison professor of genetics Sean Carroll said genes are not lost during the evolutionary process.
""We can now see the potential that has been concealed,"" Carroll said, explaining that the ability for birds to grow teeth has remained hidden within their DNA.
UW-Madison professor of biochemistry Michael Cox said that most evolution occurs this way.
""Instead of losing a gene, the regulation just changes so that the gene is not expressed during development,"" Cox said. ""The gene or genes remain in the genome, and may be manifested again if a mutation occurs that alters its regulation.""
Cox's comments and the most recent poultry findings recall studies done in the 1970s, in which researchers found developing chickens could be coaxed into growing mammal-like teeth if mouse oral tissue was introduced to their mouths. Carroll said that he doubts the mutation would happen outside a laboratory environment, but the studies help show researchers that these genes and traits can be pulled out of hibernation with certain stimuli.So where did the genes for these teeth come from? They could be relics of the chickens' reptilian ancestry. Carroll said that strong evidence in the fossil record supports the theory that birds evolved from dinosaurs.
The Journal Sentinel reported that birds are believed to have branched off from dinosaurs around 70 to 80 million years ago, trading their teeth for beaks in the process. Dormant genes can come back after longer periods of time; the molar growth in the mouse-chicken study harkens back to a 300-million-year old link between mammals and birds.
The study highlights a key aspect in trait evolution: It all comes down to development.
""All changes in form are changes that occur in development,"" Carroll said.
When it comes to a possible attack by tooth-ridden fowl, worries can be put to rest, since this mutant strain is rare and evolution has yet to make any poultry a threat.\
