Abstract
Human X chromosome has a unique biology that was shaped by its evolution as the sex chromosome shared by males and females. The differential behaviour of the two X chromosome of female cells has biological implications. During the long evolutionary process of humankind, the X chromosome has generated and recruited a disproportionately high number of functional retro-posed genes where as the autosomes experienced tower gene turnover. Recent enquiries have revealed a surprisingly large number of naturally occurring anti-sense transcripts, but their functions remain largely undiscovered. A well documented case occurs in X inactivation, the mechanism by which X-linked gene expression is equalized between XX females and XY males. The anti-sense gene determines X chromosome choice and represses the non-coding silencer. This process of chromosome inactivation (XCI) is a remarkable example of long range, mono-allelic gene silencing and facultative heterochromatin formation. The X chromosome inactivation is initiated from X inactivation centre (XIC), usually found near the centromere. The inactivated X chromosome usually lies along the edge of the interphase nucleus in tightly condensed states. An effect of hormonal factors on the frequency of sex chromatin has been a subject matter of importance since long. The present study was conducted to evaluate the prevalence of sex chromatin and its spatial organization within the nucleus among Bengalee Hindu caste females of different age groups. Buccal smear samples were collected from 150 females belonging to five different reproductive stages of their life- pre-menarchial, post menarchal, pregnant, lactating and menopausal 30 samples were chosen from each of these groups. The remits indicated differential prevalence of sex chromatin among the participants at different reproductive stages. The present study demonstrated that the prevalence of sex chromatin was significantly lowest p<0.001) and highest (p<0.001) among the pre-menarchial females and lactating mothers respectively. On the other hand, the menopausal women revealed significantly lower prevalence (p<0.001) of sex chromatin compared to the participants of rest of the reproductive categories. Furthermore, the present study revealed that the spatial organization differ significantly among different reproductive stages. These results suggested possible association between the presence of steroid hormone receptors and the prevalence of sex chromatin.
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