Recently someone told me, in most case, total expression of genes of each sample in RNA-seq shoud be similar.
I summed all gene's fpkm values belong to each sample in my RNA-seq results， but the fpkm sums are quite different.
sample1 sample2 sample3 sample4 sample5 sample6 fpkm_sum 479064.4143 499710.9913 559446.653 389748.5528 376967.4209 396236.5871
Then I downloaded some FPMK results form TCGA (samples are belong to one project). results are like this:
sample1 sample2 sample3 sample4 sample5 sample6 fpkm_sum 416526.1892 288256.1748 330630.1418 502633.3157 381001.8546 284932.5021
I'm confused now, FPKM sum of each samples in RNA-seq should be similar to or not? Please tell me.
Thanks a lot.