Hypothetical scheme of the origin of Chromatin Diminution (CD) a genome reduction during evolution occurs in germ line cells and somatic line cells; genes responsible for meiosis are located in the part of chromosomes that is not subject to genome reduction b genome reduction during evolution occurs in germ line cells and somatic line cells; during genome reduction the genes responsible for meiosis are located in the part of chromosomes that is subject to reduction; as a result, the offspring become sterile due to the absence of genes controlling meiosis c genome reduction occurs only in somatic line cells while preserving the original genome in germ line cells; during chromatin diminution the genes responsible for meiosis are located in parts of the chromosome that are subject to reduction during chromatin diminution; but they are retained in the chromosomes of germline cells. The offspring are viable. Chromatin diminution does not affect development processes.