Friday, 31 May 2013

How do Parkinson's researchers discover new knowledge? Part 4

Part 1:

Part 2:

Part 3:

TOOL 3 – Expression plasmids

To understand a gene you must understand the protein it generates; the criminal has to be investigated to understand the extent of his crimes.

What does the mutated protein do?

Genes contain the information required to build proteins; genes are said to “express” or manufacture proteins and they can do this because different combinations of DNA subunits link together specific amino acids, which make up proteins.

Is it possible to express the mutated protein to help study it? Researchers use necklace-like circular DNA molecules called expression plasmids to express genes. First a gene is copied by PCR and then inserted into the expression plasmid (like adding links to a necklace). The expression plasmid is transferred into cells where it tricks the cell into expressing the gene it carries.

TOOL 4 – Green fluorescent protein

In every cell proteins are busy carrying out all of the essential functions needed to keep the cell alive. Different proteins work in different areas of the cell; imagine a cell is like a house and each room requires different furniture and appliances. If a protein is to be understood one of the crucial things to know is where in the cell it does its job. Normally, when you look at cells down a microscope they are colourless so how do we pin point one colourless protein out of thousands in a cell?

A special protein found in jellyfish called green fluorescent protein (or GFP) glows green when a particular wavelength of light is shone on it. By following the green glow you know where GFP is. Can this help locate other proteins? GFP is expressed from a GFP gene and, like all genes, the GFP gene is made up of A, T, C and G subunits. This is important; it means that a gene from a person (e.g. the gene we found mutated in the Parkinson’s family) can be attached to the jellyfish GFP gene to form a hybrid gene and therefore a hybrid protein: one half human and the other half jellyfish. Therefore, wherever the human protein goes the GFP protein goes too; when an expression plasmid containing the GFP hybrid gene is introduced into cells a particular part of the cell will glow green, demonstrating the human protein does its job there.

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