Abstract
A sequential multiprobe fluorescence in situ hybridization technique was developed to study the 13, 18, 21, X and Y chromatid segregation in human lymphocytes anaphases cultures without antimitotic treatment. This method was used to know if exist any different chromosomes segregation in lymphocytes from Down syndrome patients and compared it with controls. The results show that the prevalent sequence of centromere separation was X, 13, 21, Y and 18 in Down syndrome patients and Y, 13, X, 21 and 18 in controls. Chromatid segregation in early anaphase was asynchronic for all chromosome pairs studied. Late anaphase showed a frequency of non-disjunction of 4.5% in the controls, affecting only chromosomes 18 and Y; in the Down syndrome patients, the frequency was higher (20.3%) and affected all chromosomes studied. This technique could be applicated to know the incidence of non disjunction in couples with repetitive abortions or in cases with different aneuploidies in the offspring.