Príons apontam para um novo tipo de evolução não darwinista

sexta-feira, fevereiro 17, 2012

Prions point to a new style of evolution

Updated 15:31 16 February 2012 by Andy Coghlan

Magazine issue 2852.

THE rogue proteins behind variant CJD, the human form of mad cow disease, have revealed their benign side. Prions, it seems, lie at the heart of a newly discovered form of near-instant evolution that provides life with a third way to adapt to potentially lethal environments. Crucially, it involves neither genetic nor epigenetic changes to DNA.

The conventional view is that new traits can only evolve if DNA itself changes in some way. The classic way to do this is by mutating the genetic code itself. More recently, researchers have discovered that molecules can clamp onto DNA and prevent some parts of the sequence from being read, leading to genetic changes through a process that is known as epigenetics.

Yeast breaks the mould. In challenging conditions, it can instantly churn out hundreds of brand-new and potentially lifesaving proteins from its DNA, all without changing the genes in any way. Instead, yeast alters the way genes are read. The tiny fungi convert a special type of protein called Sup35 into a prion.

Sup35 normally plays an important role in the protein production line. It makes sure that the ribosomes within cells, in which the proteins are built, start and stop reading an RNA strand at just the right points to generate a certain protein.

When Sup35 transforms into a prion, it no longer performs that role. With this quality control missing, the entire gene sequence is read as it spools through the ribosome. This generates new proteins from sections of RNA that are usually ignored (see diagram).

The result is that the yeast generates a hotchpotch of brand-new proteins without changing its DNA in any way. Within that mix of new proteins could be some that are crucial for survival.

Susan Lindquist at the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, first saw this process, which she calls "combinatorial evolution", in 2004, while studying lab-grown Baker's yeast (Saccharomyces cerevisiae).

"We've been saying this is really cool and a way of producing new traits for years, but other people have said it's a disease of lab yeast," she says.

Now she's proved the sceptics wrong by demonstrating beyond doubt that the same process happens in nature too. She has seen it at work in 255 of 700 natural yeasts she and her colleagues have studied (Nature, DOI: 10.1038/nature10875).

Lindquist grew the yeast in a hostile environment - either oxygen-depleted or abnormally acidic, for example - and then exposed the survivors to a chemical that destroys prions. Many colonies withered, showing that the prions were responsible for their competitive edge.

Read more here/Leia mais aqui: New Scientist



A cada dia que passa, mais a evolução, como conceito científico, vai se distanciando da visão de Darwin do século 19. Complexidade e mais complexidade, fenômenos evolucionários ainda não entendidos pelos cientistas levanta perguntas, que não são feitas pela Nomenklatura científica porque vai demonstrá-la desnudada nas suas afirmações dogmáticas sobre a origem das espécies:



e outras...

Srs. está mais do que na hora de dizer adeus a Darwin, sem medo de ser feliz. Eu já disse adeus a Darwin em 1998 após ler o livro A Caixa Preta de Darwin (um livro adotado em escolas e universidades), de Michael Behe, e vi o quanto fui engabelado na minha formação educacional que me enfiou a teoria da evolução goela abaixo sem nenhum questionamento crítico.

O pior de tudo é que esta DOUTRINAÇÃO IDEOLÓGICA DO MATERIALISMO FILOSÓFICO continua sendo prática diária nas salas de aulas de ciência. Chamam isso de educação. Eu chamo de DESONESTIDADE EDUCACIONAL. 171 Epistêmico. Tudo isso feito para defender uma posição que sempre teve dificuldades no contexto de justificação teórica desde 1859.