Monday, January 26, 2009

Chromosomal analysis by Chromosome Painting

Chromosome painting is a powerful tool for chromosomal analysis. The technique of labeling chromosomes with different colored dyes is known as chromosome painting. This is carried out by the technique known as FISH or Fluorescent In Situ Hybridization.

FISH has been used to detect the location of specific genomic targets using probes that are labeled with specific fluorochromes. The technique allows detection of simple and complex chromosomal rearrangements. In addition, complex chromosomal abnormalities can be identified that could not be detected by the conventional cytogenetic banding techniques.

In the July 26,1996 issue of Science, Schrock, et al. reported the development of a similar technique that allows the multi-color detection of human chromosomes. The technique is known as Multiplex-fluorescence In Situ Hybridization (M-FISH). The technique has been accomplished by allowing 24 combinatorially labeled chromosome-painting probes to hybridize with human chromosomes. Then, the emitted spectrally overlapping chromosome specific DNA probes are resolved using computer separation (classification) of the spectra.

This technique can be used for detection of chromosomal abnormalities. On the basis of the location of the probes used, the size of the alteration can be estimated. In addition, the developed technique provides information that complements conventional banding analysis. With the use of this technique, it is easy to identify the presence of numerous chromosomal translocations and unambiguously identify structural alterations including a giant marker chromosome (marl) in the aneuploid breast cancer cell line, SKBR3. The application of these techniques should facilitate analysis of chromosomal aberrations and genetic abnormalities in various human diseases including cancer. These new techniques will undoubtedly find wide clinical applications, and specifically the characterization of complex karyotypes will complement standard cytogenetic studies.

The basic steps in the technique of chromosome painting are:

a) Collection of nucleic-acid sequences specific for each of the individual chromosomes. These sequences should not be present in other chromosomes.

b) The sequences specific for each chromosome are converted into probes by labeling them with fluorescent dyes. Probes for each chromosome should be labeled with different (colors) fluorescent dyes.

c) In situ hybridization of each probe with the target chromosomes within the cells. Simultaneous hybridization with all probe set results in a chromosome spread preparation, in which each of the set of homologous chromosomes appears a different color when viewed with a fluorescent microscope.

Tags: Bio Technology, Bio Genetics, Chromosomal Techniques

Related Posts by Categories