Why needing normalization technique?

[mountain]

Why needing normalization technique??

Why do we have to normalize an experiment for instance in microarray or transfection?


Thanks.

 

[Monique]

To account for differences in signal caused by systematic errors, like dye labelling efficiencies, dye scanning properties, power of the two lasers, print tip effects, spatial effects (for the microarray) and transfection efficiencies, cell survival, etc (for transfection).

 

[mountain]

I have searched for a general discussion about normalization, but could not find any good ones. Do you have any useful links?

 

[Monique]

Here is a link for microarrays http://www.dnamicroarrays.info/Data_Norm.html

The commonly used normalization procedures are Total Intensity normalization, LOWESS Normalization, Mean centering, Ratio Statistics, Standard deviation regularization.

 

[misskitty]

Stupid Question ( I seem to be good at asking them): what are microarrays and transfection?

 

[Monique]

Those are not stupid questions ;)

With a microarray you can measure gene expression. It is based on hybridizing the expressed gene products (RNA that has been converted into cDNA) to probes on a chip. When hybridization occurs you get a signal. In this way you can analyze all the genes in a genome (~30,000 in the case of humans).

Transfection is the method of introducing DNA into eukaryotic cells. It can also be used to measure gene expression, where a gene promoter is cloned in front of a reporter gene.