abnormal rDNA copy number progressively decreasing rDNA copy number during successive meiotic generations A physical cellular phenotype in which the number of ribosomal DNA (rDNA) repeats present in the rDNA arrays on chromosome III is significantly lower than the range in wild type cells, and continues to decrease over successive meiotic generations (i.e. cycles of mating, meiosis, sporulation, spore germination and vegetative growth). 2015-08-17T14:04:34Z progressively shortening rDNA through meiotic generations midori FYPO:0004826 progressively decreasing rDNA copy number over successive meiotic generations progressively decreasing ribosomal DNA copy number during successive meiotic generations