G-banding, G banding or Giemsa banding is a technique used in cytogenetics to produce a visible karyotype by staining condensed chromosomes. It is useful for identifying genetic diseases through the photographic representation of the entire chromosome complement.
What is the importance of chromosome banding?
Chromosome banding allows the identification of chromosome deletions, duplications, translocations, inversions, and other less common chromosome abnormalities.
What helps in studying chromosomes banding pattern?
Chromosome banding refers to alternating light and dark regions along the length of a chromosome, produced after staining with a dye. … Specific staining protocols include C-banding and staining of the nucleolar organizing regions (NORs) using a silver stain (Ag-NOR).
What are the different types of banding?
The different types of banding are G-banding, reverse-banding, C-banding, Q-banding, NOR-banding, and T-banding. Giemsa stain is used in G-banding whereas quinacrine is used in Q-banding.
What is reverse banding?
Definition. (cytogenetics) A chromosome banding method that employs Giemsa staining technique that produces bands complementary to G-bands. Supplement. Cytogeneticists use banding techniques to determine the characteristic pattern of light and dark bands on a chromosome under a microscope.
What type of dye is used in G banding?
Bright field G-bands
These G-bands are most commonly used. They take their name from the Giemsa dye, but can be produced with other dyes. In G-bands, the dark regions tend to be heterochromatic, late-replicating and AT rich. The bright regions tend to be euchromatic, early-replicating and GC rich.
How do you do G banding?
- Make air-dried preparations by dropping small droplets of cell suspension on the slides and blowing dry. …
- Incubate slides in Coplin jars (5-6 per jar) in 2XSSC at 60-65°C for 1 1/2 hrs.
- Transfer all slides to 0.9% NaCl at room temperature. …
- Stain 4-6 minutes in trypsin-Giemsa solution (below).
Why is trypsin used in G-banding?
Trypsin partially digests some of the chromosomal proteins, thereby relaxing the chromatin structure and allowing the Giemsa dye access to the DNA. In general, heterochromatic regions, which tend to be AT-rich DNA and relatively gene-poor, stain more darkly in G-banding.
What causes the dark banding on a chromosome?
One of the basic chromosomal banding patterns is that produced by Giemsa reagent, a DNA stain applied after mild proteolytic digestion of the chromosomes. This reagent produces patterns of light-staining (G-light) regions and dark-staining (G-dark) regions.
What are the bands on a chromosome called?
The ends of the chromosome are called telomeres. Each chromosome arm is divided into regions, or cytogenetic bands, that can be seen using a microscope and special stains. The cytogenetic bands are labeled p1, p2, p3, q1, q2, q3, etc., counting from the centromere out toward the telomeres.