Genetic modification of mammalian genome at chromosome level

The review is concerned with a progress in genetic modification of a mammal ian genome in vitro and in vivo at chromosomal level. Recently three new ap proaches for the chromosome biotechnology have been developed: Using Cre/lo xP-system a researcher is able to produce targeted rearrangements of whole chromosomes or their segments or particular genes within the genome, and th c rt fore to modify the set, position and copy number of the endogenous ele ments of the genome. Mammalian artificial chromosomes (MACs) provide a poss ibility to introduce into genome relatively large segments of alien chromos ome material, either artificially constructed ol derived fi om the genome o f different species. Using ES-somatic cell hybrids allows to transfer whole chromosomes or their fragments between different genomes within and betwee n species. Advantages and limitations of these approaches are discussed.