DNA Content and Area of Sex Chromatin in Subjects with Structural and Numerical Aberrations of the X Chromosome

Abstract

Sex chromatin deoxyribonucleic acid (SC/DNA) content (determined by Feulgen-photometry) was higher in cultured cell nuclei derived from five women with presumptive iso-chromosomes for the long arm of the X than from five normal women. The mean SC/DNA values from subjects with deleted long arm or short arm iso-chromosome X; deletion of the short arm of X and from lymph node cultures of a subject with a ring X were significantly lower than the control values. SC/DNA from subjects with XY/XXY, XXXY and XXXXY sex chromosome constitutions did not differ from control values. In oral mucosa nuclei the mean SC/DNA and sex chromatin area from the subjects with structurally abnormal X’s also showed a correlation between X chromosome size and SC/DNA or SC/area but in this technically less suitable tissue variability was greater and the differences not statistically significant. These findings indicate that: 1. Only one X chromosome forms sex chromatin. 2. When a structural abnormality of the X is present it is always the abnormal one which becomes positively heteropycnotic. 3. It is probably all, or at least the major portion of the X which forms sex chromatin. 4. The multiple sex chromatin bodies formed in cells with supernumerary X’s contain average amounts of DNA. 5. Visual impression of sex chromatin “size” (staining intensity and area integrated) can be confirmed objectively.