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11.4: Functional Genomics – Determining Function(s)

Having identified putative genes within a genome sequence, how do we determine their function?  Techniques of functional genomics are an experimental approach to address this question.  One widely used technique in functional genomics is called microarray analysis (Fig. 11.9).  Microarrays can measure the abundance of mRNA for hundreds or thousands of genes at once.  The abundance of mRNA of a particular gene is usually correlated with the activity of that gene.  For example, genes that are involved in neuronal development likely produce more mRNA in brain tissue than in heart tissue.  We can therefore learn about the relationship between particular genes and particular processes by comparing transcript abundance under different conditions. This can identify tissue specific expression (e.g. the nerve/heart example above), as well as differences in temporal expression (development), or exposure to external agents (eg, disease, hormones, drugs, etc.).

Figure 11.9: An example of a type of DNA microarray.  Fluorescently labeled molecules derived from the transcripts of two tissue samples are hybridized to immobilized DNA molecules on the surface of an array.  The labeled molecules bind in proportion to their abundance in the original tissue samples.  The amount of green or red fluorescence at each spot can be measured using filters for the appropriate wavelengths. Thus, spots on the micoarray that are more green than red represent genes that are more abundant in the tissue sample from which green-labeled molecules were derived. (Original-Deyholos-CC:AN)