The misuse of the three-point cross for estimating chiasma interference.
The building of genetic maps in diploid organisms by crosses between different genotypes and estimation of recombination frequencies from the obtained segregation data has been successfully used since a very young step in the birth of genetics. The three-point cross methodology has facilitated this task and has demonstrated at the same time that genetic distances are not additive, as some recombinant products are not recognised in the progeny. Three-point cross also allows to examine if chiasma interference exists and its evaluation. Here I show that the classical method of this estimation is erroneous and inevitably determines the apparition of a spurious, positive interference, which has been claimed to be an almost general phenomenon. Interference can only be estimated from a precise knowledge of the number of crossing over events occurring in meiocytes.
Casares
Pelayo
P
Area de Genetica Universidad de Oviedo, Spain. pcg@uniovi.es
D000818:Animals; D003434:Crossing Over, Genetic; D005838:Genotype; D006801:Humans; D008540:Meiosis; D008957:Models, Genetic; D011995:Recombination, Genetic; D012641:Selection, Genetic