The key difference between chromosome banding and chromosome painting is that chromosome banding is a staining technique that displays regions of chromosomes in distinguishable dark and light bands, but chromosome painting is a hybridization technique in which specific regions or segments of chromosomes are painted with sequence-specific fluorescently labelled probes.
In cytogenetics, it is necessary to produce a visible karyotype of an organism in order to identify chromosomes and their aberrations. Chromosome banding and chromosome painting are two cytogenetic techniques that aid in visualizing chromosomes. Both techniques are useful in identifying genetic disorders.
CONTENTS
1. Overview and Key Difference
2. What is Chromosome Banding
3. What is Chromosome Painting
4. Similarities Between Chromosome Banding and Chromosome Painting
5. Side by Side Comparison – Chromosome Banding vs Chromosome Painting in Tabular Form
6. Summary
What is Chromosome Banding?
Chromosome banding is a staining technique that displays alternating light and dark bands or regions along the length of a chromosome. A band refers to a part of a chromosome that is clearly distinguishable from its adjacent segments by appearing darker or lighter. In order to produce dark and light bands, it is necessary to stain the chromosomes using a suitable dye such as fluorescent dye quinacrine or Giemsa stain.
There are several types of chromosomal banding techniques. Among them, Q-banding, Reverse (R) banding and G-banding are generalized banding techniques. G banding technique uses a stain called Giemsa stain, and it stains AT-rich regions of heterochromatic regions in darkly stained bands and GC rich euchromatic regions in lightly stained bands. R banding is the reverse of G banding, and it stains GC rich regions in dark bands and AT-rich regions in light bands. Q banding, on the other hand, utilizes fluorescent dye quinacrine and it stains chromosomes in a yellow fluorescence of differing intensity. C banding technique is another banding technique that stains centromere regions. Moreover, T banding technique visualizes telomere regions.
Figure 01: Chromosome Banding
The banding pattern is unique to organisms. Hence, these unique banding patterns are important in identifying chromosomes and detecting chromosomal aberrations (chromosome breakage, loss, duplication, translocation or inverted segments).
What is Chromosome Painting?
Chromosome painting is a technique in which specific regions or segments of chromosomes are painted with sequence-specific probes which are fluorescently labelled. Therefore, chromosomal painting is always coupled with in situ FISH technique. It is totally based on the molecular hybridization with sequence-specific probes on chromosomes. Hence, it needs specific probes in order to hybridize the target chromosomes or chromosome regions.
Figure 02: Chromosomal Painting
Moreover, this technique initially requires the denaturation of the target chromosomal DNA which are in the metaphase. Secondly, the hybridization step takes place with probes. Once probes find their complementary sequences, they hybridize with the specific regions of the chromosome. We can easily observe the hybridized sites using autoradiography or immunofluorescence. Preparation of probes, denaturation, hybridization and visualization are the four main steps involved in chromosomal painting.
Concerning applications, chromosomal painting is useful when identifying chromosomal rearrangements, breakpoints and in the determination of extrachromosomal materials. Moreover, it is a powerful tool in the exact localization of different gene sequences of chromosomes at the microscopic level. Furthermore, chromosomal painting is helpful in identification of genes for desired characters in the chromosomes.
What are the Similarities Between Chromosome Banding and Chromosome Painting?
- Chromosome banding and chromosome painting are two techniques used in the cytogenetic analysis.
- Both techniques visualize chromosomes usually in metaphase.
- These techniques can identify normal chromosomes and aberrations.
- Moreover, these techniques are really useful in identifying genetic disorders.
What is the Difference Between Chromosome Banding and Chromosome Painting?
Chromosome banding is a staining technique that displays parts of chromosomes in dark and light bands, which are distinguishable. Meanwhile, chromosome painting is a hybridization technique that paints specific regions of chromosomes with sequence-specific probes which are fluorescently labelled. So, this is the key difference between chromosome banding and chromosome painting. Furthermore, chromosome banding produces alternating dark and light bands along the length of the chromosome, while chromosome painting produces fluorescently labelled regions of chromosomes.
Moreover, chromosome banding depends on the ability of the chromosomal DNA to stain with a dye, while chromosome painting depends on the molecular hybridization with sequence-specific probes on chromosomes. This is an important difference between chromosome banding and chromosome painting. Besides these, unlike chromosome banding, chromosome painting technique requires sequence-specific fluorescently labelled probes.
Summary – Chromosome Banding vs Chromosome Painting
Chromosome banding and chromosome painting are two technique used to visualize chromosomes, usually in metaphase. Both techniques help to identify numerical and structural chromosomal aberrations and genetic diseases. Chromosome banding is a staining technique that displays specific regions of chromosomes in dark and light bands, which are distinguishable. Meanwhile, chromosomal painting is a type of hybridization technique that visualizes specific regions of chromosomes due to the hybridization with fluorescently labelled sequence-specific probes. So, this is the key difference between chromosome banding and chromosome painting.
Reference:
1. Thomas, et al. “Chromosome Painting: A Useful Art.” OUP Academic, Oxford University Press, 1 Sept. 1998, Available here.
2. “G Banding.” Wikipedia, Wikimedia Foundation, 19 Jan. 2020, Available here.
Image Courtesy:
1. “NHGRI human male karyotype” By National Human Genome Research Institute – (Public Domain) via Commons Wikimedia
2. “Karyotype of giraffe (Giraffa camelopardalis)” By Anastasia I Kulemzina, Polina L Perelman, Darya A Grafodatskaya, Trung T Nguyen, Mary Thompson, Melody E Roelke-Parker and Alexander S Graphodatsky – Kulemzina AI, Perelman PL, Grafodatskaya DA, et al. Comparative chromosome painting of pronghorn (Antilocapra americana) and saola (Pseudoryx nghetinhensis) karyotypes with human and dromedary camel probes. BMC Genetics. 2014;15:68. doi:10.1186/1471-2156-15-68. (CC BY 2.0) via Commons Wikimedia