Meiosis consists of beautifully co-ordinated series of events in space and time to facilitate an orderly reduction of chromosome number and the segregation and recombination of chromosomes. That the structure and behaviour of chromosomes at meiosis are controlled genetically or genotypically was first pointed out by Darlington (1932). There are good reasons to support that the behaviour of chromosomes at meiosis is determined by a complicated interaction of genes they bear and the environment.