Sex-chromatin in Iranian newborn females

Area of Science:

• Cytogenetics
• Neonatal Biology
• Human Genetics

Background:

• Sex chromatin, or Barr bodies, are inactivated X chromosomes visible in interphase nuclei.
• Understanding Barr body expression in neonates is crucial for developmental biology.
• Previous studies suggested a rise in sex-chromatin-positive cells within the first few days of life.

Purpose of the Study:

• To investigate the incidence of sex-chromatin-positive cells in buccal smears of newborn females during the first five days of life.
• To compare Barr body frequency in term infants, small-for-date premature infants, and appropriate-for-gestational-age premature infants.
• To compare neonatal Barr body incidence with that of older female children.

Main Methods:

• Buccal smears were collected from three groups of newborn females (term, small-for-date premature, appropriate-for-gestational-age premature) and a control group of older females.
• Smears were stained with aceto-orcein to visualize sex-chromatin-positive cells (Barr bodies).
• The incidence of sex-chromatin-positive cells was quantified in each group.

Main Results:

• No significant difference in sex-chromatin-positive cell incidence was observed among the three newborn female groups.
• The mean incidence of sex-chromatin-positive cells in neonates was lower than in the older female control group.
• The mean incidence on the fifth postnatal day did not reach the 17% observed in older controls, contrasting with some prior reports.

Conclusions:

• The incidence of sex-chromatin-positive cells in newborn females is lower in the neonatal period compared to older females.
• Barr body expression in neonates may follow a different developmental trajectory than previously suggested.
• Further research is warranted to elucidate the dynamics of X-chromosome inactivation in early human development.