History of radiation genetics: light and darkness

Purpose: To review the history of radiation effects in germ cells and to attempt to discern future directions. Materials and methods: Review of published papers. Results: Recent mouse studies using microarray-based comparative genomic hybridization techniques revealed that germline mutations would occur much less frequently than would be expected from the results of past studies which used specific locus tests. The mean induction rate of deletion mutations was about 1%/genome per Gy. In other words, one out of 100 offspring following a parental (possibly only paternal) exposure to 1 Gy may be expected to have one deletion. This means that at low doses, the genetic risk of radiation is so small and difficult to detect, especially when we learn that our genomes are not perfect and carry as many as on average 80 inactivated genes under heterozygous conditions. Nevertheless, any radiation-induced de novo mutations can be deletions which may involve haploid-sensitive genes, and hence can be a threat to health. Conclusion: Although powerful methods such as whole-genome-sequencing techniques have become available to detect radiation effects in human germ cells, the mutation induction rate in the genome now appears to be much lower than was previously thought. Consequently, detecting radiation effects in human germ cells still remains a difficult task.