Deletion mapping of the human X chromosome

In an attempt to determine the location of genes on the human X chromosome, clinical and cytogenetic findings in 3 non-mosaic females with deleted X chromosomes were compared. A hitherto largely unrecognized difficulty in mapping deletions is the possibility that these may be interstitial rather than terminal. The delimitation of cytogenetic abnormalities requires banded mitoses of exceptionally good quality, and even then appearances may admit of more than one interpretation. Some previously held notions on karyotype-phenotype correlations must at present be regarded as questionable.