ABSTRACT
With the rediscovery of Mendel’s laws, determination of DNA as the genetic material, resolution of the double-helix structure of DNA and its implications for genetic behavior during the past century, biology research has entered the era of genomics, for which studies are emphasized at the genomewide or biological process-wide levels. One of the basic, but essential prerequisites for such studies is the availability of techniques for preparation of DNA that is megabase-sized from organisms of interest, considering the fact that conventional DNA extraction procedures (including in-house reagents and commercial kits) usually result in the isolation of DNA under 120 kb in size. Recent development of procedures for isolation of megabase-sized DNA fragments has opened new avenues for genomics research on a variety of biological organisms. The potential use of megabase DNA fragments includes the analysis of long-genome spanning genes (e.g., the mammalian dystrophin gene that has a transcript of >2000 kb), characterization of gene regulatory elements and clusters of genes (e.g., plant disease resistance genes), development of large-insert genomic DNA libraries [1-5], genome physical mapping [6-10], long-range genome analysis [11,12], map-based or positional cloning of genes and quantitative trait loci (QTLs) [13], large-scale genome sequencing [2,14], and microbe genome karotyping [15-17]. Furthermore, a recent study [3] showed that DNA molecules contained in a genome are structured as linear “jigsaw puzzle” and that the content, array, and interaction of the fundamental functional elements constituting the DNA jigsaw puzzle structure are responsible for the abundance, diversity, and complexity of living organisms, indicating the importance of long-range genome analysis in biology research.
