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Someone with two X chromosomes (such as the majority of human females) has only one Barr body per somatic cell, while someone with one X chromosome (such as most human males) has none. Mammalian X-chromosome inactivation is initiated from the X inactivation centre or Xic , usually found near the centromere . [ 6 ]
The metaphase chromosomes are treated with trypsin (to partially digest the chromosome) and stained with Giemsa stain. Heterochromatic regions, which tend to be rich with adenine and thymine (AT-rich) DNA and relatively gene-poor, stain more darkly in G-banding.
Some staining methods are based on this property. Those stains excluded by the living cells but taken up by the already dead cells are called vital stains (e.g. trypan blue or propidium iodide for eukaryotic cells). Those that enter and stain living cells are called supravital stains (e.g.
Toluidine blue is often used to identify mast cells, by virtue of the heparin in their cytoplasmic granules. [3] It is also used to stain proteoglycans and glycosaminoglycans in tissues such as cartilage. The strongly acidic macromolecular carbohydrates of mast cells and cartilage are coloured red by the blue dye, a phenomenon called metachromasia.
All cells of a given species package the same regions of DNA in constitutive heterochromatin, and thus in all cells, any genes contained within the constitutive heterochromatin will be poorly expressed. For example, all human chromosomes 1, 9, 16, and the Y-chromosome contain large regions of constitutive heterochromatin. In most organisms ...
A "vital dye" or stain is a dye capable of penetrating living cells or tissues without causing immediate visible degenerative changes. [26] Such dyes are useful in medical and pathological fields in order to selectively color certain structures (such as cells) in order to distinguish them from surrounding tissue and thus make them more visible ...
The basic number of chromosomes in the somatic cells of an individual or a species is called the somatic number and is designated 2n. In the germ-line (the sex cells) the chromosome number is n (humans: n = 23). [4] [5] p28 Thus, in humans 2n = 46. So, in normal diploid organisms, autosomal chromosomes are present in two copies.
[2] [3] Carbol fuchsin is used as the primary stain dye to detect acid-fast bacteria because it is more soluble in the cells' wall lipids than in the acid alcohol. If the bacteria is acid-fast the bacteria will retain the initial red color of the dye because they are able to resist the destaining by acid alcohol (0.4–1% HCl in 70% EtOH). [ 4 ]