a method of genetic analysis of lower eucaryote organisms. It is based on the simultaneous study of the genotypes of all four haploid products of the meiosis of an individual diploid cell.

The tetrads (groups of four spores) formed in some fungi, algae, and mosses remain within the membrane of the parent cell after meiosis. By isolating the spores of each tetrad during tetrad analysis, the genotype of the parent diploid cells may be determined and the behavior of individual genes and centromeres and of entire chromosomes in meiosis may be traced. The tetrad analysis of mosses helped prove that the Mendelian division of genes results from meiosis and is a biological law, not a statistical one.

The use of tetrad analysis in modern genetics is based on the fact that any pair of allelic genes yields a division of 2:2 in tetrads. In some experiments, deviations from this division have been observed. When these deviations are very rare they may be detected and studied solely by means of tetrad analysis.