Hi,

I am using genespring for microarray data analysis. After normalisation and statistical analysis I got the result file of the genes and their expression intensity values. I have 2 replicated of control and 2 replicates of diseased sample. Once I observed the normalised value of control replicate samples, I found out they are almost the same. There is just a difference of positive and negative sign. I also observed that expression in both the control replicates are always the opposite sign(-/+).

Can anyone help me on how the replicates are always of the opposite sign in controls