MUTAGENESIS AND GENETIC HOMEOSTASIS IN HI GHER ORGANISMS

Structural genes and genetic regulatory sites occupy merely a small sp ace in the eukaryotic genome; the remaining space presents various unc oding sequences. Genomic reorganizations, i. e. changes in the mutual arrangements of nucleotide sequences in DNA, appearance of new sequenc es and disappearance of old ones, have occurred in evolution many time s. The genomic reorganizations reflect biological mutagenesis which ca nnot basically depend on primary DNA damages. Ionizing radiation and t raditional chemical mutagens are unable to induce great genomic reorga nizations. The cellular genetic apparatus alone plays a key role in ma intaining genetic homeostasis and preventing genomic reorganizations. There are some examples of genomic reorganizations in eukaryotes, incl uding those resulting in human hereditary diseases. There are evidence for that chromosomal aberrations occur in the minor site of a genome, which is topologically related to the nuclear matrix.