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
and Cy
,
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