THE SUPPRESSION OF GENE CONVERSION AND INTRAGENIC CROSSING OVER IN ASCOBOLUS IMMERSUS: EVIDENCE FOR MODIFIERS ACTING IN THE HETEROZYGOUS STATE

[摘要] Four distinct systems cv1, cv2, cv4 and cv6 behaving as monogenic factors have been found in the stock 28 of Ascobolus immersus . They each specifically suppress gene conversion in a spore pigmentation gene (respectively, b1, b2, b4 and b6 ). In the gene b2 , where this phenomenon was studied in most detail, the effect of cv2 on the suppression of gene conversion is almost total; intragenic recombination is very strongly diminished and crossing over is also affected. In the genes b1, b2 and b4 the suppression of conversion is observed only when the corresponding modifier ( cv1, cv2 and cv4 ) is in the heterozygous condition. It is likely that cv6 acts in the same way on b6 . cv1 and b1 on one hand, cv2 and b2 on the other, are very closely linked; no recombination was observed between these modifiers and the corresponding spore pigmentation genes. The same genetic distance is observed between the linked genes b4 and b6 and between cv4 and cv6 . This could indicate that these two modifiers are also closely linked to the corresponding genes. A possible effect of cv4 on intergenic recombination between b4 and b6 was shown: here again it acts by diminishing the frequency of recombination when cv4 is in the heterozygous state. The problem of the nature of the cv modifiers is discussed.

[学科分类] 医学（综合）