How do you determine a genes copy number?
Genes copy number is the number of copies of a particular gene in the genotype of individual.
To determine copy number various techniques are used-
1. Hybridisation- based techniques
a. Southern blotting - It is the traditional method to determine gene copy number. The principle of this technique is relies upon fragmentation of DNA with restriction endonuclease enzymes , followed by gel electrophoresis and transfer to a nylon membrane. It uses labelled DNA probe to visualize target regions. A probe that hybridizes only single DNA segment will produce single band, whereas probe that hybridizes to several similar sequences will produce multiple bands. This technique allows to determine gene copy number changes by creation of altered fragment sizes.
b. FISH- Using this technique we attach probes to part of chromosomes and observe them under fluorescence microscope. A probe is a small chemical compound made up of single-stranded DNA with fluorescent marker. It is composed in such a way that it is complementary to the piece of DNA that we want to test. There are several fluorescent markers of different colors. In situ hybridisation means binding to the site. This allows to visualize several pieces of DNA at the same time.
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