One of the following forms the basis for sex chromatin testing:

Ans. a, i.e. Barr bodyRef: Gamong 24th/ed, p392-393Barr body forms the basis for sex chromatin testing.Barr BodyWhen two X chromosomes are present in a cell (as in a normal female) one of them becomes inactivated and condensed on the nuclear membrane and is called the 'Barr body'. This process is termed as X chromosome lyonization (inactivation)Presence or absence of Barr bodies helps in ascertaining the sex of an individuals* Absence of Barr body indicates that the patient has only one X chromosome (e.g. Normal male XY or Turner's syndrome (XO)* Nuclei of cells in females (XX) contain a darkly staining Barr body that is not present in the nuclei of cells in males.* Barr bodies are most easily seen in a smear of squamous epithelial cells obtained by scraping the buccal mucosaQ* Barr bodies react differently to histological stains and are best seen as dark staining bodies within the nucleus of non- dividing interphase cells.