Molecular Genetics

Facts

Certain chemical treatments of mammalian chromosomes yield differentially stained regions on chromosomes. The patterns obtained depend on the treatment used.

C-banding stains centromeres. R-banding is the reverse of C-banding and stains non-centromeric regions in preference to centromeres (left upper image from rev). G-banding is obtained with Giemsa stain (left lower). It yields a series of lightly and darkly stained bands (right, image from http://www.lumc.nl/rep/1050/ima/812170411232537/812170414122537.jpg). Q-banding is a fluorescent pattern obtained using quinacrine for staining. The pattern of bands is very similar to that seen in G-banding.

Interpretations

• The reproducible patterns of light and dark bands serve as signposts to identify position on the morphological chromosome.
  

Further information

• The patterns of G- and Q- bands on a human chromosome are sufficiently unique to allow that chromosome's unambiguous identification. Best banding is obtained with prophase chromosomes since these have not yet fully condensed
• An arrayed set of banded chromosomes is called a karyotype and can be used to screen for chromosome rearrangements.
• G-, Q-, and R- bandings are not observed with plant chromosomes.
• Banding patterns appear related to base composition and chromosome loop structure.
• Additional types of banding are also used. For example: N-banding stains locations of (GAR)n triplet repeats in wheat and barley (ref1, ref2 ).
  

This is page 11322 of Molecular Genetics by Ulrich Melcher, © 1997, 1998, 1999, 2001, 2009