Ty1 insertions in intergenic regions of the genome of Saccharomyces cerevisiae transcribed by RNA polymerase III have no detectable selective effect

The retrotransposon Ty1 of Saccharomyces cerevisiae inserts preferentially into intergenic regions in the vicinity of RNA polymerase III-transcribed genes. It has been suggested that this preference has evolved to minimize the deleterious effects of element transposition on the host genome, and thus to favor their evolutionary survival. This presupposes that such insertions have no selective effect. However, there has been no direct test of this hypothesis. Here we construct a series of strains containing single Ty1 insertions in the vicinity of tRNA genes, or in the rDNA cluster on chromosome XII, which are otherwise isogenic to strain 337, containing zero Ty1 elements. Competition experiments between 337 and the strains containing single Ty1 insertions revealed that in all cases, the Ty1 insertions have no selective effect in rich medium. These results are thus consistent with the hypothesis that the insertion site preference of Ty1 elements has evolved to minimize the deleterious effects of transposition on the host genome.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72266/1/S1567-1356_03_00199-5.pd

Origin of Life

The evolution of life has been a big enigma despite rapid advancements in the fields of biochemistry, astrobiology, and astrophysics in recent years. The answer to this puzzle has been as mind-boggling as the riddle relating to evolution of Universe itself. Despite the fact that panspermia has gained considerable support as a viable explanation for origin of life on the Earth and elsewhere in the Universe, the issue remains far from a tangible solution. This paper examines the various prevailing hypotheses regarding origin of life like abiogenesis, RNA World, Iron-sulphur World, and panspermia; and concludes that delivery of life-bearing organic molecules by the comets in the early epoch of the Earth alone possibly was not responsible for kick-starting the process of evolution of life on our planet.Comment: 32 pages, 8 figures,invited review article, minor additio

Simulating Evolution’s First Steps

Abstract. We demonstrate a simple artificial chemistry environment in which two small evolutionary transitions from the simplest self-replicators to larger ones are observed. The replicators adapt to increasingly harsh environments, where they must synthesise the components they need for replication. The evolution of a biosynthetic pathway of increasing length is thus achieved, through the use of simple chemical rules for catalytic action.