Genetic Variation in Linkage Values

Abstract

GENETICS: DETLEFSEN AND CLEMENTE below 50%',. At a still greater distance it rises again,, thus undergoing oscillatory changes above and below 50%0. With increase of distance the oscillations become less marked, until at a sufficiently great distance the cross-over ratio settles down at 50%0 (or in close approximation to that value). Obviously, for interference extending over long distances, the serial order of the genes would not be given by the increasing values of the crossover ratios with the end genes. Genes farther from the end would often have a lower cross-over ratio with it than genes nearer to it. Chromosome maps constituted, like those in use in Drosophila, on the basis that increased ratios mean greater distances, would give incorrect and inconsistent results. However, maps showing the correct order of the genes could still be constructed by considering successively genes having crossover ratios less than the number of units of interference. Cross-over ratios above 50% have not thus far been certainly found in nature. If such should be found, a high degree of interference is indicated, and it is to be anticipated that there will occur also the other relations shown in this paper to accompany high interference. Details are given in a paper to be published in Genetics. GENETIC VARIATION IN LINKAGE VALUES1