CONCERTED EVOLUTION OF REPETITIVE DNA-SEQUENCES IN EUKARYOTES

A large fraction, sometimes the largest fraction, of a eukaryotic geno me consists of repeated DNA sequences. Copy numbers range from several thousand to millions per diploid genome. All classes of repetitive DN A sequences examined to date exhibit apparently general, but little st udied, patterns of ''concerted evolution. ''Historically, concerted ev olution has been defined as the nonindependent evolution of repetitive DNA sequences, resulting in a sequence similarity of repeating units that is greater within than among species. This intraspecific homogeni zation of repetitive sequence arrays is said to take place via the poo rly understood mechanisms of ''molecular drive.'' The evolutionary pop ulation dynamics of molecular drive remains largely unstudied in natur al populations, and thus the potential significance of these evolution ary dynamics for population differentiation is unknown. This review at temps to demonstrate the potential importance of the mechanisms respon sible for concerted evolution in the differentiation of populations. I t contends that any natural grouping that is characterized by reproduc tive isolation and limited gene flow is capable of exhibiting concerte d evolution of repetitive DNA arrays. Such effects are known to occur in protein and RNA-coding repetitive sequences, as well as in so-calle d ''junk DNA,'' and thus have important implications for the different iation and discrimination of natural populations.