Robertsonian translocations are the most common chromosomal rearrangements in humans, with an incidence of approximately 1/1000 individuals(Therman et al. 1989). They arise through exchanges between the short arms of acrocentric chromosomes: 13, 14, 15, 21, and 22. Exchanges within these five chromosomes may form ten nonhomologous Robertsonian translocations, but their distribution is highly nonrandom with the predominance of rob(13;14) (75 %) and rob(14;21) (10%)(Thermanetal.1989).Thesetwo,most common