[Meiotic crossing over--not the only source of recombinants in man]

On the basis of chiasma distributions along bivalents in human male meiosis, genetic lengths were counted for several chromosomal segments. These estimates appeared to be lower than the corresponding genetic lengths produced in the recombination analysis. When al so cytological distances and number of markers used in multilocus mapping were taken into account, the regression estimates of genetic lengths were shown to satisfactorily fit the observed values. This indicates that mitotic crossingover, genetic conversion, mutation and errors in allel's identification in addition to meiotic crossingover, appear to contribute to the observed genetic maps. It is suggested that these namely events, rather than the typing errors suggested by Morton (1991), seem observed over those predicted on the basis of chiasma counts.