ORGANIZATION OF MUTATIONS ALONG THE GENOME - A PRIME DETERMINANT OF GENOME EVOLUTION

Recent advances in molecular mutagenesis reveal that two of the mechan isms which contribute to mutagen-induced point mutations, the frequenc y of induced DNA damage and the repair rate of this damage, vary consi derably along the genome. At a grosser level of genomic resolution, cy togeneticists now distinguish several classes of chromosome bands alon g human chromosomes. The hot spots for X-ray induced breaks (chromosom e mutations) occur in certain band classes, while the hot spots for mi tomycin C-induced exchanges or melphalan-induced breaks occur in other band classes. Knowledge of these mutation patterns is modifying our c oncepts of genome evolution.