Repetitive Sequences in the Human Genome

Abstract

Publisher Summary Twenty-five percent of human DNAconsists of repetitive DNA sequences. A general outline of the chromosomal organization of these repetitive sequences is discussed in the chapter. The working hypothesis is that certain classes of human repetitive DNA sequences “encode” the information necessary for defining genomic structure. Using a combination of biochemical, computational, and recombinant DNA approaches, the organization of interspersed, centromeric, and telomeric repetitive DNA in the human genome has been investigated. The distribution of interspersed repeats can be adequately described by models that assume a random spacing, with an average distance of 3 kb. This observed distribution for the integration of interspersed repetitive DNA is the expected result for the sequences that transpose randomly throughout the genome. However, local regions of “preference” or “exclusion” for the integration of repetitive DNA are suggested by the data. Research has isolated three recombinant DNA clones of human repetitive DNA sequences that hybridize specifically to the heterochromatic positions, lqh, 9qh, and 16qh, respectively. These locations were determined by fluorescent in situ hybridization and confirmed by DNA hybridizations to human chromosomes sorted by flow cytometry.