Normalisation

The purpose of normalisation is to remove any of the non-biological, systematic effects arising in a microarray experiment, i.e. human, and technological errors. There are two types of error that methods proposed so far aim to correct: Spatial bias is mainly technologically related. Small errors that occur in the microarray robot, (e.g unevenly washing of the chip, inserting the chip at a slight angle in the scanner etc.), may have a large impact on the results. Many hours of printing might also alter the shape and size of the print-tips, and thus cause spatial patterns on the array.

Dye bias appear from the fact that the two dyes used, Cy$ 3$ and Cy$ 5$, have slightly different physical properties, and the react slightly different to photo-bleaching, an effect that occurs in multiple scannings of the array, [3]. Environmental factors such as the level of ozone, is also a contributing factor.



Subsections

Bjørn Kåre Alsberg 2006-04-06