Comparison of G-, Q-, and R-banding in 28 cases of chromosomal abnormalities.

Twenty-eight cases of chromosomal abnormalities were ascertained using G-banding. Seventeen of these had structural abnormalities of a complex nature and are discussed in detail. An independent assessment of chromosome abnormalities was carried out using sequential Q- and R-banding. In no case was there a difference in the identification of the abnormal chromosome, but in two cases a more precise localization or definition of the abnormality was obtained from the R-banded cells. In one case the initial diagnosis of the terminal deletion was altered to interstitial deletion; in the second case a break point in one chromosome involved in a reciprocal translocation was found to be in a different band by R-banding. In several others better delineation of break points or confirmation of complex abnormalities was obtained from the R-banded cells. R-banding was especially helpful in the localization of break points because of the color differentiation obtained with acridine orange. Q-banding was not found to have added any additional information. It was concluded from this study that the use of both G-banding and R-banding in complex abnormalities proved worthwhile.