Circular genetic maps

The widespread occurrence of genetic circularity suggests a selective advantage to map circularity per se. Circularity permits gene clustering relations not possible in linear maps; that is, every gene in a circular map can have two nearest map neighbors, two next nearest, etc. It seems possible that map circularity is a consequence of the selective forces responsible for the clustering of genes of related function. Certain features of the pattern of crossing-over in various fungi suggest that circularity of linkage maps is there to be found. A concurrence of high frequencies of second-division segregation and negative chromatid interference across the centromere, both of which phenomena have been reported, is a feature of a simple hypothetical crossover pattern that generates circular linkage maps.