In a recent PNAS, Barry Hall has a paper demonstrating directed mutagenesis (he's calling

---
Master Index Current Directory Index Go to SkepticTank Go to Human Rights activist Keith Henson Go to Scientology cult

Skeptic Tank!

In a recent PNAS, Barry Hall has a paper demonstrating directed mutagenesis (he's calling it selection-induced mutation now) in yeast. He shows that the mutation in question occurs more often when adaptive than otherwise, that the mutation rate increases at that locus only and that the mutation is time- dependent not replication dependent. He also shows that the appearance of the mutations cannot be explained by phenotypic lag (i.e. the mutation happened a while back but the phenotype hadn't been expressed yet.) The importance of the paper lies primarily in the fact that he has shown this process (directed mutagenesis) occurs in an organism distantly related to the one he and Cairns originally showed it in (_E. coli_). This could either be a case of convergent evolution or evidence that this process is ancestral (i.e. present in the common ancestor to prokaryotes (like _E. coli_ ) and eukaryotes (like yeast). The mechanism for directed mutagenesis is still unknown. REFERENCE Hall, 1992, Selection-induced mutations occur in yeast, PNAS 89: 4300-4303

---

E-Mail Fredric L. Rice / The Skeptic Tank