Gene Expression

The holistic approach to functional genomics relies on high-throughput methods for measuring gene expression. This is basically the amount of protein (coded for by the gene) present in a cell at a specific moment. The existing methods for measuring gene expression are based on two biological assumptions:

1.

Transcription level of genes indicates their regulation: Since protein is generated from a gene in a number of stages (e.g. transcription, splicing, synthesis of protein from mRNA), regulation of gene expression can occur at many points. This assumption means that most regulation is done only during the transcription phase (i.e. genes that have gotten past the transcription phase will most likely be expressed).

2.

Only genes which contribute to organism fitness are expressed. This means that genes which are irrelevant to the organism's function are not expressed.

Relying on these assumptions, we can conclude that detecting changes in gene expression level provides clues on the function of its product.