Development and Analysis of a DNA Array

The process of carrying out a DNA array can be divided into (1) sample preparation, 

DNA samples for genomic studies are extracted directly from cells (section 6.1). For expression studies, RNA is isolated and then converted to cDNA in a process called reverse transcription (section 6.2.5). Samples must be fluorescently labelled, denatured to single strands and usually partially digested to shorter DNA fragments. 

A few p,L of sample solution is either dropped onto the array or passed over it in a flow cell. The hybridisation process takes 12 to 16 hours, usually at elevated temperatures of around 60 °C. After hybridisation, several washing steps must be performed. 

The developed array must then be scanned. Macroarrays can be interrogated with a conventional scanner. Microarrays require more dedicated equipment for example laser fluorescence confocal microscopes. The scan can then be analysed with specialised software. Often results are compared using electronic libraries. 

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