Cytogenetic assays for genotoxic agents

The induction of genetic damage has clear and dramatic implications for human health, with teratogenic, mutagenic, cataractogenic and carcinogenic consequences resulting from cellular chromosomal alterations in appropriate tissues. When analysing the potential of an agent to initiate genetic damage or in evaluating possible incumbent genomic damage a variety of complementary assays may be employed. These apply to cells in vitro, to in vivo assessments involving small mammals and most importantly to derived human cells and tissues including those of ocular origin. Cytogenetic assays have the important advantage that they enumerate damage at the level of the individual cell. Assays involving the examination of chromosomal aberrations at mitosis, of cells prior to mitosis using the technique of premature chromosome condensation, of micronuclei in post-mitotic cells and of sister chromatid exchanges will be described. The development of human chromosome specific probes and fluorescent in situ hybridisation (FISH) techniques combine the resolution of molecular biology with classical cytogenetics in a powerful approach to defining genomic change and its consequences. These techniques and assays can be further augmented by in situ cytometry such that overall a number of parameters can be quantified involving cellular kinetics, clastogen and/or aneugen definition and ultimately the establishment of dose response relationships. A rational basis for avoidance or control, for intervention or for defining probable cause of the role of genotoxicants in the development of human disease can then be established.