Technical Replicates vs Biological Replicates - (May/12/2015 )

I have tried running rt-pcr with technical triplicates & Biological triplicates. I compared the ct values of the house keeping gene (GADPH); the ct values are close for the technical replicates. 

However, when I compared the ct values between the biological replicates, the ct value of GADPH varies about 5 ct. 

Is this suppose to happen? Do biological replicates show such a huge variations between ct values?

Thanks in advance for any advice.

Yes, it can.

Micronoxic conditions can influence GAPDH levels. Probably will have more effect on some cell type than others.

I always harvest my cells at around the same density and add the same volume of media to the well. So the depth of the media is constant.