[BioC] asymmetry in up and down regulation

[Chris Paulse]

Figure 5 in the recent Nucleic Acids Research 2003, Vol. 31, No. 4 e15
(http://nar.oupjournals.org/cgi/content/full/31/4/e15/GNG015F5) shows an 
interesting asymmetry in the distribution of fold changes for non-spiked in 
genes.  Can anyone comment on the reason for this?  Here, dChip has the 
least amount of bias.

Thanks,
Chris