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Comparative Genomic Hybridisation (CGH) (CAT#: STEM-GT-0016-WXH)

Introduction

CGH is a method of molecular cytogenetic testing that detects chromosomal copy number variants (portions of the genome where sections of genes are doubled or tripled) without the need for cell culturing. It was first developed to identify such changes in tumours.
CGH differs from other methods of cytogenetic testing in that it does not rely on a specific target, nor does it require previous knowledge of the region under examination. Instead, CGH can quickly scan a whole genome for chromosomal imbalances and it is useful in cases where the diagnosis is not known. One limitation of CGH is the size of the genetic alteration that it can identify; the resolution of CGH is poor at approximately 5–10 megabases.




Principle

CGH uses 2 genomes; the test sample and a control, both of which are fluorescently labelled to differentiate between the two. The two samples are denatured and mixed together, allowing hybridisation of metaphase chromosomes. The intensity of the fluorescent signal of the labelled test DNA relative to the control DNA can then be plotted along each chromosome, which shows the loss or gain of genetic material and allows identification of any copy number variants.

Applications

Detects chromosomal copy number variants without the need for cell culturing.
Identifying gains and losses of a specific chromosomal region within the whole genome.

Procedure

1. DNA extraction and digestion.
2. Labelling Test DNA with Cy5, labelling reference DNA with Cy3.
3. Combine equal amount of DNA and hybridisation.
4. Scanning and image.

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