which = protein?


"Determining a patient's KRAS status should now form part of our standard diagnostic practice as the test identifies the patients who will benefit most from Erbitux," added Bokemeyer.

The KRAS gene codes for a protein involved in the the epidermal growth factor receptor (EGFR) pathway, which plays a role in the control of cell growth, proliferation, and differentiation, and cancer risk.
We can't tell, this requires specialized knowledge, grammatically it could be many things in the previous sentence, such as
a protein etc ...

the epidermal growth factor receptor (EGFR)
the epidermal growth factor receptor (EGFR) pathway
the whole previous sentence (less probable here, because of the plural, "which play," required by the "gene codes")
I'm quite sure you're correct. The sentence threw me at first, until I realized that "codes" is the verb. It's a usage which is unfamiliar to me, but it makes sense. I guess it means that a function of this particular gene is to extablish the exact chemical structure of this particular protein.

- A.
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