Molecular Techniques In Pathology

Molecular techniques are methods of analysing the expression of particular genes which may be involved in the initiation or progression of cancer.

Microarray

A microarray contains hundreds of different DNA probes collected into small, microscopic spots. A single array can therefore be used to examine hundreds or thousands of genes from a single sample, and determine their expression.
The binding of complementary DNA to a probe causes a detectable change in the array (frequently a colour change). The gene expression of an entire tumour can then be viewed to see how it has altered from baseline.

Tissue Microarray

A tissue microarray is a block in which numerous tissue samples are arranged in an array pattern. The block can be sliced with a microtome numerous times, and the samples treated with different methods. For instance, if one hundred breast tumours had a sample placed into a tissue microarray, immunohistochemistry could be performed on them all to see the differences in ERBB2 expression.

Reverse Transcriptase Polymerase Chain Reaction (RT-PCR)

RT-PCR is used to measure the amount of RNA within the cell. Through the use of reverse transcriptase enzyme, a target strand of RNA can be transformed into a DNA strand, for which polymerase chain reactions are available.
By heating DNA, it denatures into separate strands. By using primers to identify the target strands, heat resistant DNA polymerases duplicate the strand and double the quantity of the desired DNA sequence. By repeatedly cooling and heating the DNA, the target DNA strand can be amplified and detected more readily.
RT-PCR is useful for identifying the RNA expression of a single gene.

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