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Title: Epidermal Growth Factor Signalling Pathway Question? Post by: dbassan on Nov 30, 2013 I'm going through medical exam sample papers and am really stuck on one question, which involves a diagram and multiple choice answers. I've searched in many textbooks and online, and yet can't get much info on it.
More than one answer may be correct for any line. Diagram: (http://i287.photobucket.com/albums/ll160/JOSHoward/DSC02657.jpg) The diagram above illustrates a signalling pathway that is hyperactive in breast cancer cells. Each label A-L indicates a protein. Identify the protein(s) that are described below. 1. One protein whose absence will tend to cause cells to divide (that is, the product of a tumour suppressor gene). 2. One protein that is not synthesized by the parental, non-tumour cells but which is often expressed by breast cancer cells. 3. One protein that binds to DNA. (I believe this is L, but maybe others also?) 4. One protein that is often mutated in cancers in such a way that its ability to activate the downstream target is maintained for a much longer time than is the case for the normal protein. 5. One or more proteins (without kinase catalytic activity) that bind to a second, target protein. The target protein, a kinase, is inactive unless the indicated protein(s) is/are found. Any help, or a point in the right direction, would be greatly appreciated! Title: Epidermal Growth Factor Signalling Pathway Question? Post by: davashkai on Nov 30, 2013 1. K - Rb is one of the classic example of a tumor suppressor
2. Not sure about this one, but I'd guess A cause there's no real reason to have EGF in tissue that's not actively dividing? 3. L works, E2F is a transcription factor so it needs to bind to DNA 4. E - Ras fits this, it's a GTPase that deactivates itself, and this function is often lost due to a mutation so it stays active (another classic example) 5. I - CDKs (cyclin dependent kinases), as their name implies, don't do anything unless there is a cyclin bound. A might also be correct, as its receptor (EGFR) is also a kinase (it kinases itself, but i guess that still counts). The MAP kinases probably don't fit here because the question specifies "without catalytic activity." |