Molecular biology is an area of biology concerned with the process of gene transcription to yield RNA, the translation of RNA into proteins and the role those proteins play in cellular function. Since around 1960, molecular biologists have developed methods to identify, isolate, and manipulate molecular components in cells including DNA, RNA, and proteins.
Several techniques used in the field of molecular biology are described below.
- Polymerase chain reaction (PCR) – This is one of the most important techniques used in molecular biology and is basically used to copy DNA. PCR allows a single DNA sequence to be amplified into millions of DNA molecules. PCR can also be used to introduce mutations within the DNA or introduce special restriction enzyme sites. In addition, PCR is used to determine whether a certain DNA fragment exists in a cDNA library. Different types of PCR include reverse transcription PCR (RT-PCR) for amplification of RNA and quantitative PCR (QPCR) to measure the amount of RNA or DNA present.
- Expression cloning – This technique helps scientists understand the protein function. The DNA that codes for a particular protein is cloned or copied using PCR into an expression vector called a plasmid. The plasmid is introduced to either an animal cell or a bacterial cell. This plasmid has promoter elements that can stimulate high expression of the desired protein so that its enzymatic activity can then be examined.
- Gel electrophoresis – This is another important technique used in molecular biology to separate DNA, RNA, and proteins based on their size by applying an electric field as the DNA is run through agarose gel.
- Macromolecule blotting and probing – Processes such as southern blotting, northern blotting, western blotting and eastern blotting are used to transfer DNA or RNA proteins onto a blotting membrane (often after gel electrophoresis) so they can be stained or radioactively labelled and then visualized.
- Arrays – A DNA microarrays or DNA chip is a collection of DNA spots mounted on a solid surface such as a microscope slide that can be used to simultaneously quantify protein expression levels across a large number of genes. The technique can also be used to genotype various different genomic regions.