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What happens in the laboratory?

In a genetics laboratory, specific tests will be performed depending on the reason the patient has been referred.

The test may look for:

Laboratory techniques for investigating DNA and chromosomal alterations

A range of techniques are used by genetic testing laboratories to investigate the possibility that an individual has a genetic or chromosomal alteration. Technological advancements have increased the capacity of most laboratories, such that many more analyses can be undertaken simultaneously. The development of the microarray has meant that smaller genetic changes can now be detected, revealing disorders that would have been undetectable until recently. Laboratory tests in genetics are particularly amenable to the fast pace of technology developments. Therefore, even if a genetic or chromosomal change cannot be found now, there is a possibility that new techniques will enable scientists to find it in the future.

The table below summarizes the main techniques used for analysis, each of which has a dedicated page explaining the technique in detail.




Separating individual chromosomes and arranging them systematically for examination

Fluorescence in situ hybridisation (FISH)

Checking a specific chromosomal region for deletions or rearrangements


Increasing the amount of DNA in the sample

Gel electrophoresis

Visualising DNA which has undergone PCR

Array Comparative genomic hybridisation (aCGH)

Checking the whole genome for large deletions or duplications (copy number variation)

Quantitative fluorescence - polymerase chain (QF-PCR)reaction (QF-PCR) Controlled PCR that allows the number of copies of a chromosome region to be assessed. This is used in the rapid prenatal test for common chromosomal trisomies such as Down syndrome

Multiplex Ligation-dependent Probe Amplification (MLPA)

Detecting deletions or duplications of part of a gene

DNA sequencing (Sanger)

Checking for alterations in the order of bases in the genetic code

Next generation sequencing (NGS)

Large-scale DNA sequencing producing vast amounts of data in a single test.