Concerted evolution of tRNA genes: Intergenic conversion among three unlinked serine tRNA genes in S. pombe

In many cases the multiple genes coding for one specific tRNA are dispersed throughout the genome. The members of such a gene family nevertheless maintain a common nucleotide sequence during evolution. A major mechanism contributing to this concerted evolution is intergenic conversion. Here we show that it occurs between three tRNA genes of related sequence residing on different chromosomes of Schizosaccharomyces pombe. Sequence analysis of converted genes indicates that blocks of a minimal length of 18-33 bp and of a maximal length of 190 bp can be transferred from one gene to the other. During meiosis the frequency of these transfers lies in the order of 10(-5) per progeny spore. Information transfer between any two members of the gene family occurs in both directions.