Methodology

Lymphocytes from a peripheral blood sample are stimulated to grow with phytohemagglutinin, cultured for 72 hours and treated to obtain elongated chromosomes. Following arrest of cell division with Colcemid, chromosomes are stained by the G-banding method. The chromosome number is determined by microscopic analysis and these cells are examined for the presence or absence of detectable structural rearrangements. Two banded karotypes are prepared and 30 or more metaphases are analyzed to rule out the possibility of mosaicism of 10% at the 95% confidence level. Additional techniques are employed when required.