TARSIUS DELTA-GLOBIN AND BETA-GLOBIN GENES - CONVERSIONS, EVOLUTION, AND SYSTEMATIC IMPLICATIONS

  • 5 January 1989
    • journal article
    • research article
    • Vol. 264  (1) , 68-79
Abstract
Comparisons between duplicated genes have shown that gene conversions play an important role in the evolution of multigene families. Previous comparisons have documented in the recently duplicated .gamma.-fetal globin genes of catarrhine primates, over 15 separate conversions affecting extensive stretches of coding and noncoding sequences. In the present study, .delta.- and .beta.-globin genes from a lower primate Tarsius syrichta, and the .delta.-globin gene of the Asian great ape, Pongo pygmaeus, have been isolated and sequenced. Comparisons of these sequences with other primate .delta. and .beta. sequences confirmed a previously reported conversion in an anthropoid ancestor and revealed additional conversions in basal primate, stem haplorhine, tarsier, and early lemur lineages. Conversions between primate .delta.- and .beta.-globin genes contrast with those found in the .gamma.-genes and that .delta.-.beta. conversions appear much less frequently and are more restricted to regions conserved by selection (i.e. coding and 5''-regulatory sequences). These differences indicate that soon after a duplication occurs, conversions can be quite frequent and encompass extensive portions of the duplicated region. With time, sequence differences accumulate, particularly in noncoding regions, and limit both the frequency and size of the conversions. Sequences conserved by selection accumulate differences more slowly and are therefore subject to gene conversions for a longer period of time. Both unconverted and converted sequences were consistent in supporting the placement of tarsier with anthropoids.