“W. Ford Doolittle’s reticulated tree, or net, stresses the importance of horizontal gene transfer in archaeal and bacterial evolution.”
HORIZONTAL GENE TRANSFER
http://physorg.com/news89292896.html
Does evolution select for faster evolvers?
“It’s a mystery why the speed and complexity of evolution appear to increase with time. For example, the fossil record indicates that single-celled life first appeared about 3.5 billion years ago, and it then took about 2.5 billion more years for multi-cellular life to evolve. That leaves just a billion years or so for the evolution of the diverse menagerie of plants, mammals, insects, birds and other species that populate the earth. New studies by Rice University scientists suggest a possible answer; the speed of evolution has increased over time because bacteria and viruses constantly exchange transposable chunks of DNA between species, thus making it possible for life forms to evolve faster than they would if they relied only on sexual selection or random genetic mutations. “We have developed the first exact solution of a mathematical model of evolution that accounts for this cross-species genetic exchange,” said Michael Deem, the John W. Cox Professor in Biochemical and Genetic Engineering and professor of physics and astronomy. The research appears in the Jan. 29 issue of Physical Review Letters.
Past mathematical models of evolution have focused largely on how populations respond to point mutations – random changes in single nucleotides on the DNA chain, or genome. A few theories have focused on recombination – the process that occurs in sexual selection when the genetic sequences of parents are recombined. Horizontal gene transfer (HGT) is a cross-species form of genetic
transfer. It occurs when the DNA from one species is introduced into another. The idea was ridiculed when first proposed more than 50 years ago, but the advent of drug-resistant bacteria and subsequent discoveries, including the identification of a specialized protein that bacteria use to swap genes, has led to wide acceptance in recent years. “We know that the majority of the DNA in the genomes of some animal and plant species – including humans, mice, wheat and corn – came from HGT insertions,” Deem said. “For example, we can trace the development of the adaptive immune system in humans and other jointed vertebrates to an HGT insertion about 400 million years ago.”
The new mathematical model developed by Deem and visiting professor Jeong-Man Park attempts to find out how HGT changes the overall dynamics of evolution. In comparison to existing models that account for only point mutations or sexual recombination, Deem and Park’s model shows how HGT increases the rate of evolution by propagating favorable mutations across populations. Deem described the importance of horizontal gene transfer in the work in a January 2007 cover story in the Physics Today, showing how HGT compliments the modular nature of genetic information, making it feasible to swap whole sets of genetic code – like the genes that allow bacteria to defeat antibiotics. “Life clearly evolved to store genetic information in a modular form, and to accept useful modules of genetic information from other species,” Deem said.
Source: Rice University
http://experts.rice.edu/ExpertDetail.cfm?EID=2491&Type=E
http://mwdeem.rice.edu/
http://mwdeem.rice.edu/mwdeem/deem_papers.html
contact : mwdeem [at] rice [dot] edu
ABSTRACT
http://arxiv.org/format/q-bio.PE/0612027
Phase Diagrams of Quasispecies Theory with Recombination and Horizontal Gene Transfer / Authors: Jeong-Man Park, Michael W. Deem
“We consider how transfer of genetic information between individuals influences the phase diagram and mean fitness of both the Eigen and the parallel, or Crow-Kimura, models of evolution. In the absence of genetic transfer, these physical models of evolution consider the replication and point mutation of the genomes of
independent individuals in a large population. A phase transition occurs, such that below a critical mutation rate an identifiable quasispecies forms. We generalize these models of quasispecies evolution to include horizontal gene transfer. We show how transfer of genetic information changes the phase diagram and mean fitness and introduces metastability in quasispecies theory, via an analytic field theoretic mapping.”
ASSISTED LEARNING
http://www.mayanmajix.com/art1699.html
Nobel Prize genius Crick was high on LSD when he discovered the secret of life
BY ALUN REES / August 8, 2004
“FRANCIS CRICK, the Nobel Prize-winning father of modern genetics, was under the influence of LSD when he first deduced thedouble-helix structure of DNA nearly 50 years ago. The abrasive and unorthodox Crick and his brilliant American co-researcher James Watson famously celebrated their eureka moment in March 1953 by running from the now legendary Cavendish Laboratory in Cambridge to the nearby Eagle pub, where they announced over pints of bitter that they had discovered the secret of life. Crick, who died ten days ago, aged 88, later told a fellow scientist that he often used small doses of LSD then an experimental drug used in psychotherapy to boost his powers of thought. He said it was LSD, not the Eagle’s warm beer, that helped him to unravel the structure of DNA, the discovery that won him the Nobel Prize.
Despite his Establishment image, Crick was a devotee of novelist Aldous Huxley, whose accounts of his experiments with LSD and another hallucinogen, mescaline, in the short stories The Doors Of Perception and Heaven And Hell became cult texts for the hippies of the Sixties and Seventies. In the late Sixties, Crick was a founder member of Soma, a legalise-cannabis group named after the drug in Huxley’s novel Brave New World. He even put his name to a famous letter to The Times in 1967 calling for a reform in the drugs laws. It was through his membership of Soma that Crick inadvertently became the inspiration for the biggest LSD manufacturing conspiracy-the world has ever seen the multimillion-pound drug factory in a remote farmhouse in Wales that was smashed by the Operation Julie raids of the late Seventies.
Crick’s involvement with the gang was fleeting but crucial. The revered scientist had been invited to the Cambridge home of freewheeling American writer David Solomon a friend of hippie LSD guru Timothy Leary who had come to Britain in 1967 on a quest to discover a method for manufacturing pure THC, the active ingredient of cannabis. It was Crick’s presence in Solomon’s social circle that attracted a brilliant young biochemist, Richard Kemp, who soon became a convert to the attractions of both cannabis and LSD. Kemp was recruited to the THC project in 1968, but soon afterwards devised the world’s first foolproof method of producing cheap, pure LSD. Solomon and Kemp went into business, manufacturing acid in a succession of rented houses before setting up their laboratory in a cottage on a hillside near Tregaron, Carmarthenshire, in 1973. It is estimated that Kemp manufactured drugs worth Pounds 2.5 million an astonishing amount in the Seventies before police stormed the building in 1977 and seized enough pure LSD and its constituent chemicals to make two million LSD ‘tabs’.
The arrest and conviction of Solomon, Kemp and a string of co-conspirators dominated the headlines for months. I was covering the case as a reporter at the time and it was then that I met Kemp’s close friend, Garrod Harker, whose home had been raided by police but who had not been arrest ed. Harker told me that Kemp and his girlfriend Christine Bott by then in jail were hippie idealists who were completely uninterested in the money they were making. They gave away thousands to pet causes such as the Glastonbury pop festival and the drugs charity Release. ‘They have a philosophy,’ Harker told me at the time. ‘They believe
industrial society will collapse when the oil runs out and that the answer is to change people’s mindsets using acid. They believe LSD can help people to see that a return to a natural society based on self-sufficiency is the only way to save themselves. ‘Dick Kemp told me he met Francis Crick at Cambridge. Crick had told him that some Cambridge academics used LSD in tiny amounts as a thinking tool, to liberate them from preconceptions and let their genius wander freely to new ideas. Crick told him he had perceived the double-helix shape while on LSD.
‘It was clear that Dick Kemp was highly impressed and probably bowled over by what Crick had told him. He told me that if a man like Crick, who had gone to the heart of human existence, had used LSD, then it was worth using. Crick was certainly Dick Kemp’s inspiration.’ Shortly afterwards I visited Crick at his home, Golden Helix, in Cambridge. He listened with rapt, amused attention to what I told him about the role of LSD in his Nobel Prize-winning discovery. He gave no intimation of surprise. When I had finished, he said: ‘Print a word of it and I’ll sue.’