RSS
Evolution Without Genes
Most explanations of Darwinian evolution refer to genetic material as the manner in which changes are passed down to one’s descendants. Now, a study by Jiali Li of the Scripps Institute in Florida finds that prions, the proteins that cause diseases like mad cow disease evolve in response to their environment. Prions have no genes, no chromosomes, and no DNA or RNA at all!
Prions are rogue version of a protein called PrP. Like all proteins, they are made up of chains of amino acids that fold into a complex three-dimensional structure. Prions are versions of PrP that have folded incorrectly and this misfolded form, called PrPSc, is social, evangelical and murderous. It converts normal prion proteins into a likeness of its abnormal self, and it rapidly gathers together in large clumps that damage and kill surrounding tissues.
Li has found that variation can creep into populations of initially identical prions. Their amino acid sequence stays the same but their already abnormal structures become increasingly twisted. These “mutant” forms have varying degrees of success in different environments. Some do well in brain tissue; others thrive in other types of cell. In each case, natural selection culls the least successful ones. The survivors pass on their structure to the “next generation”, by altering the folds of normal prion proteins.
Scientists are not ready to classify prions as living things, even though this discovery may lead to some refinements in the definition of life. Link
Zavatone
tipple
hugh
