Expected Frequencies of Chromosome Associations in Tetraploids with Random Chiasma Formation.

N tetraploids the degree of multivalent formation at meiosis is often used as a 'wit erion of homology between the chromosome sets and gives information on the genetic control of chromosome association. Where the chiasma frequency of each association can be recorded in a number of cells, the observed association frequencies could be profitably compared with frequencies expected, assuming they arise from the random formation of chiasmata between the four chromosomes. Even where the chiasma frequencies are not easily obtained, it would be an advantage to have some idea of the association frequencies expected on this basis. Some formulae have been derived and tables prepared for this purpose.