[Mutagenesis and genetic homeostasis in higher organisms]

Structural genes and genetic regulatory sites occupy merely a small space in the eukaryotic genome; the remaining space presents various uncoding sequences. Genomic reorganizations, i.e. changes in the mutual arrangements of nucleotide sequences in DNA, appearance of new sequences and disappearance of old ones, have occurred in evolution many times. The genomic reorganizations reflect biological mutagenesis which cannot basically depend on primary DNA damages. Ionizing radiation and traditional chemical mutagens are unable to induce great genomic reorganizations. The cellular genetic apparatus alone plays a key role in maintaining genetic homeostasis and preventing genomic reorganizations. There are some examples of genomic reorganizations in eukaryotes, including 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.