Chromosome banding
refers to alternating light and dark regions along the length of a chromosome, produced after staining with a dye
band
part of a chromosome that is clearly distinguishable from its adjacent segments by appearing darker or lighter with the use of one or more banding techniques
1968
year when Torbjorn Caspersson worked with plants using the highly fluorescent quinacrine mustard which produced the first reported chromosome banding patterns
1971
year when band was defined in a Paris conference as a part of a chromosome which is clearly distinguishable from its adjacent segments by appearing darker or lighter with various banding methods
importance of chromosomal banding
allows visualization of smaller pieces of the chromosome
identification of smaller structural chromosome abnormalities not visible on a routine analysis
positive bands
bands that show strong staining
negative bands
weakly staining bands
replication banding
most widely used function-based banding method
R-band DNA
replicated earlier than G-bands
G-bands
correspond to the condensed chromomeres of meiotic chromosomes
R-bands
correspond to the interchromomeric regions
G- and R-banding
*most commonly used techniques for chromosome identification (karyotyping)
or identifying abnormalities of chromosome number, trans- locations of material from one chromosome to another, and deletions, inversions or amplifications of chromosome
Two ways laboratories accomplish banding methods
optimizing the banding and staining procedures
choosing cells with longer, less condensed chromosomes during metaphase
metaphase
phase of mitosis when dye-based chromosome banding is done
methods of dye-based chromosome banding
Giemsa
Reverse
Centromere
Quinacrine
Giemsa Banding Technique
most widely used routine banding method in the United States
most commonly used stain in cytogenic analysis
G-banding
staining a metaphase chromosome with a Giemsa stain
G-banding
banding techniques that require pretrating
Reverse Banding Technique
banding technique that produce a banding pattern that is the opposite or reverse of the G-banding pattern
euchromatic regions
R-band-positive regions that are the more genetically active regions of the chromosomes
R-banding
involves pretreating cells with a hot salt solution that denatures DNA that is rich in adenine and thymine
Centromere Banding Technique
techniques that stain selective chromosome regions
Torbjorn Caspersson
cytologist that developed Q banding techniques
Nor Staining
This technique selectively stains the nucleolar organizer regions (NORs) located on the satellite stalks of the acrocentric chromosomes
chromosome painting
hybridization of fluorescently labeled chromosome-specific, composite probe pools to cytological preparations
meaning of FISH
Fluorescence In Situ Hybridization
Fluorescence In Situ Hybridization
introduced the ability to highlight inidividual genes