Repeated DNA in primates, especially in humans, will be examined by specific restriction endonuclease cleavage, by DNA sequencing and by in situ hybridization. Experiments will be designed to decide whether tandemly-repeated DNA provides genetic flexibility for driving speciation. Specifically, we will study the involvement of newly-evolved, tandemly-repeated DNA in karyotype evolution and in the formation of karyotypic abnormalities in cancer cells. We will attempt to determine how repeated DNA is involved in recombinational processes, such as unequal crossing over. Experiments will also be designed to elucidate the mechanism by which repeated DNA becomes interspersed among nonrepeated DNA. We will determine the nucleotide sequence of interspersed, repeated DNA and of its flanking sequences. Over the long-term we are interested in knowing whether repeated DNA carries recombination-promoting domains that mediate gene mobility. These experiments are now possible because we have learned approximately when newly-evolved repeated sequences (NERS) in primates were amplified, because we know that they were amplified from a "library" of ancestral repeated DNA and because the NERS can be isolated in a pure state from genomic DNA. Baboons split from guenons 8-10 million years ago. Each group of monkeys carries a characteristic 170n base pair NERS. Sequence information on NERS from several species will tell us whether amplification preceeded, coincided with or postdated speciation. The sequence of noninteger NERS will pinpoint regions of unequal crossing over. We already know regions of sequence divergence between guenon and baboon NERS. Thus, in situ hybridization using divergent portions of NERS as probes at stringent criteria will locate NERS clusters on (evolutionarily new?) chromosomes.
NIH ExPorter
NIH ExPorter