Hi Karen,

1) Grafting is the process of placing tumour cells into a host (like mice). "Post-graft" is referring to the fact that they are observing tumour cell growth 11 days after they placed these tumour cells into the mice.

2) Why A is wrong: As a transcriptional coregulator, pRB should be translocated to the nucleus upon TNFa stimulation
Why B is wrong: The Bax/Bak are part of the intrinsic apoptosis pathway. This isn't information you need to know for the MCAT but you can identify that it is wrong by the passage talking about Bax/Bak involved in the mitochondrial apoptosis pathway, which would be a process happening within the cell (intrinsic). Extrinsic pathways are triggered by things outside of a cell.

3) There is mtDNA transcription and translation occurring within the mitochondria but there is also overlap of nuclear transcription and translation and subsequent translocation to mitochondria involved in the regulation as well.

4) It involves the right combination of detergents and centrifugation to isolate proteins from the membrane vs cytosol for example. You can then do SDS-page to separate and visualize your protein of interest.

Hope this helps :)