A further improved method for identifying heteromorphism of acrocentric chromosomes.

An improved method for identifying an individual heteromorphic acrocentric chromosome, a high-resolution dual Q-R banding, is described. The acrocentrics of 550-850 band-stage prometaphase showed more distinct fluorescent heteromorphic patterns at their paracentromeric regions than those of 400 band-stage metaphase. In the two families studied, all four (two pairs of) parental prometaphase homologues in every kind of acrocentric except chromosome 22 were clearly distinguished from each other, leading to accurate determination of the parental origin of all the children's acrocentric chromosomes. The dual Q-R banding on metaphase plates could distinguish at most three of four such homologues of the parents in both families. Several possible applications of this method are discussed.