Sex chromatin

Uncultured cells have also been used to a limited extent for fetal sex determination. This Is possible because the cells can be appropriately stained and examined for the presence of sex chromatin, characteristic of female cells, and for the fluorescent Y-body, characteristic of male cells (33,34). However, these cytologic techniques are not completely reliable, and It Is still desirable to determine fetal sex by direct chromosome analysis (35). 

Mukherjee, A. B. Blattner, P. Y. and Nltowsky, H. M. Qulnacrlne Mustard Fluorescence of Sex Chromatin In Human Amnlotlc Fluid Cell Cultures". Nature (New Biol.), (1972), 235, 226-229. 

Comings, D. E. 1967. The duration of replication of the inactive X chromosome in humans based on the persistance of the heterochromatic sex chromatin body during DNA synthesis. Cytogenetics (Basel), 6 20-37. 

Klinger, H. P., H. G. Schwarzacher, and J. Weiss. 1967. DNA content and size of sex chromatin positive female nuclei during the cell cycle. Cytogenetics (Basel), 6 1-19. 

Kim S. Namekawa, S.H. Niswander, L.M. Ward, J. Lee, J.T. Bardwell, V.J. Zarkower, D. (2007b). A mammal-specific Doublesex homolog associates with male sex chromatin and is required for male meiosis. PLoS Genetics, Vol.3 No.4, pp. 559-571, ISSN 1553-7390... 

When a sample of suspect blood arrives at the laboratory, it may be useful to determine the sex of the donor (for example, in the case of criminal abortion). Low-performance older techniques (search as for the sex chromatin, Barr s body, Y-chromosome fluorescence, etc) and other methods such as the determination of sex hormone levels (progesterone/ testosterone) have been replaced by procedures for detecting sites on the X and Y chromosomes using PCR. At present, the sex determination is carried out at the same time that the genetic profile is determined when using multiplex STR kits. 

The victims of this chromosomal anomaly are often mentally retarded and sterile. The levels of urinary gonadotropins are usually high in patients with Klinefelter s syndrome, but those of 17-ketosteroids are decreased. Examination of sex chromatin is always positive. The syndrome is not rare—it has been reported in 1 of 400 newborns. Although in the typical Klinefelter syndrome, the karyotype is XXY, the syndrome has also been observed in patients with 48 chromosomes (48XXYY or 48 XXXY) and 49 chromosomes (49XXXYY or 49XXXXY). 

XXX Type of Trisomy. Patients have been observed with duplicate sex chromatin bodies in the cells of the buccal mucosa, with resistant amenorrhea, infantile external genitalia, underdeveloped breasts, and high levels of urinary gonadotropins. Chromosome studies on cultured bone marrow cells demonstrated the presence of 47 chromosomes with the XXX type of trisomy. 

Kinoshita, S., Friend, J., Thoft, R.A. Sex chromatin of donor comeal epithelium in rabbits. Invest Ophthalmol Vis Sci 21, 434-441 (1981)... 

One index of inactivation is the formation of sex chromatin bodies. In man and macaque, these bodies were identified in trophoblast cells, in 10-12-day-old blastocysts and in 16-19-day-old embryos (Glenister, 1956 Park, 1957 Liberman, 1966 Zacharov, 1968) - i.e., at the 2600-5000 cell stage (Hamerton, 1964). At the same time, sex chromatin was observed in 14% of the trophoblast cells on the 13th day of embryonic development, but is absent in the mesoderm of the chorion. 

Similar results were obtained with cats. In this case, sex chromatin was first found in trophoblastic cells of the late blastocyst stage. In embryonic cells, it was first observed during the postimplantation stage of development (Austin and Amoroso, 1957 Austin, 1962). One of the rabbit X chromosomes was heteropycnosed 2 days before implantation, at about the 400 cell stage. In the rat, this does not occur until after embryo implantation. It occurs on the 6th day of development of trophoblast cells and on the 7th day in cells of the egg cylinder (Zibina, 1964). 

Sex chromatin formation does not occur in all cells of the embryo. In 3-months-old human embryos, the sex chromatin body is present in the nuclei of somatic cells, while it is absent in oogonia and oocyte nuclei (Ohno et al. 1961). 

Fig. 67 a-c. Distribution of cells with sex chromatin in an XY/XXY mosaic human embryo, a A portion of the amnion epithelium. Left half a sex chromatin positive area right half a negative area, b Transverse section of the esophagus, c Tracing of the section with information on the incidence of sex chromatin in the epithelial layer. 7 = 0-9%, 2= 10-19%, 5 = 20-29%, 4= >30%. (After Stern, 1968)... 

Sex in animals is determined by the distribution of the special X and Y sex chromosomes in the progeny. In most species an XX combination determines the female sex and an XY combination the male. In some inborn anomalies of sex development which have been thoroughly studied in man (Klinefelter s syndrome, Turner s syndrome, and so on), as a result of failure of the chromosomes to separate, individuals wifli anomalous sets of sex chromosomes are formed (XXY, XXXY, XXX, XXXX, XXXXX, and XXXXY). In all cases with an increase in the number of X chromosomes, the supernumerary X chromosomes were found to be of the late replicating type (Grumbach et al., 1963 Rowlyetal., 1963 Atkins et al., 1963). The number of X-chromosomes with late replication in every case was one less than the total number of X-chromo-somes, and it was on account of these chromosomes that the sex chromatin of the interphase nucleus was formed. On the basis of these facts the hypothesis was put forward (Hsu, 1964a Taylor, 1964) that late replication of DNA in the chromosomes correlates or is directly connected with... 

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