[Physical mapping of the human genome: on the way to developing an optimal strategy]

Physical mapping of the human genome appears to be a complicated problem for the molecular genetics of higher organisms. The difficulties are not only due to the great amount of work to be done, but mostly due to the peculiarities of genome organization (repeated nucleotide sequences, non-clonable, methylated and toxic fragments, etc.). Mapping procedures based on molecular hybridization do not allow to obtain the unambiguous results due to the occurrence of the repeats of different types common for the genome as a whole. Giant DNA fragments (e.g. YAC--Yeast Artificial Chromosomes) undergo deletions, transformations and chimerism and cannot be the main approach for genome mapping. The new strategy for genome mapping is described with reference to the human chromosome 3--one of the largest human chromosomes. The main steps of this new strategy are the following: 1) sequencing of STS (Sequence Tagged Sites) flanking DNA rare-cutting restriction sites; 2) alignment of the STS along the chromosomal DNA (generation of the contigs) based on the comparative computer analysis of STS from the same and from the neighboring restriction sites, 3) determination of the distance between STS by hybridization of large DNA fragments with STS. In order to apply this strategy called "shot-gun sequencing strategy for long range genome mapping" a new family of vectors (SK series) specially designed for the genome cloning was constructed and the simplified inexpensive technology for preparing the jumping/linking libraries was developed. Chromosome 3 fragments were sequenced around NotI sites, and the contigs covering about 50 Mbp of genomic DNA were constructed. The perspectives for the whole human genome mapping are discussed.