2. Comparative Genomic
Hybridiztion
a molecular cytogenetic method for analysing
copy number variations (CNVs) in the DNA of
a test sample compared to a reference
sample, without the need for culturing cells.
3. The aim of this technique is to quickly and
efficiently compare two genomic DNA samples
arising from two sources and allows the
detection of losses and gains in DNA copy
number across the entire genome
4. Method
Tumour DNA is labelled with a green
fluorochrome, which is subsequently mixed
(1:1) with red labelled normal DNA and
hybridised to normal human metaphase
preparations. The green and red labelled DNA
frag-ments compete for hybridisation to their
locus of origin on the chromosomes. The
green to red fluorescence ratio measured
along the chromosomal axis represents loss or
gain of genetic material in the tumour at that
specific locus.
5.
6. Limitation
Using metaphase chromosomes for
hybridisation limits the detection of events
involving small regions (< 10–20 Mb) of the
genome.
Relatively time consuming
7. Array-CGH
Array CGH compares the patient’s genome
against a reference genome and identifies
differences between the two genomes .
Array CGH has proven to be a specific,
sensitive, fast technology.
copy number changes at a level of 5–10
kilobases of DNA sequences can be detected.
8. Method
Array CGH is based on the same principle as
conventional CGH. In conventional CGH, the
target is a reference metaphase spread. In
array CGH, these targets can be genomic
fragments cloned in a variety of vectors (such
as BACs or plasmids) and cDNAs
9.
10. Application
Cancer research
Prenatal Genetic Diagnosis
Submicroscopic aberrations (Prader–Willi
syndrome (PWS))
Genomic abnormalities in cancer
