Human Biochemistry Volume 2 - Murray R. 1993

Biochemistry of Intracellular and Intercellular Communication
Sex Hormones
Chromosomal Sex

Chromosomal sex, The first phase of sexual differentiation, is established at the time of Fertilization. This is the only immutable parameter in the aforementioned chain. In humans, the XY sex chromosome Complement determines male sex, while the combination of two X Chromosomes (XX genotype) predetermines female sex. In the absence of distinct sexual characteristics in the external genitalia or if a discrepancy between phenotypic and genotypic sex is suspected, an analysis of oral mucosal Cells, fibroblasts, or leukocytes is performed to detect the presence of Barr bodies. Barr bodies represent patches of condensed Chromatin corresponding to an inactivated X chromosome. The number of Barr bodies per Cell is one less than the number of X chromosomes it contains: for the XY genotype, it is 0; for XX, 1; for XXY, 1; and for XXX, 2. There is no evidence to suggest that Hormones can influence chromosomal Sex Determination.



Last update: 06/08/2026

Editorial and Educational Adaptation: This material has been compiled based on the primary/original source text. The project team performed an editorial review, corrected technical inaccuracies, structured sections, and adapted the content for an educational format.

What was processed:

  • elimination of formatting defects (OCR errors, structural breaks, corrupted characters);
  • editorial organization of content;
  • standardization of terminology in accordance with academic sources;
  • verification of factual statements against the original source text.

All mentions of the author, publication year, and origin of the primary text have been preserved in accordance with the source.