What are the steps in the MAPK signaling cascade initiated by activated Ras?

• A. RAF 1 -> MEK -> ERK -> Transcription factor regulation
• B. MEK -> ERK -> RAF 1 -> Transcription factor regulation
• C. ERK -> RAF 1 -> MEK -> Transcription factor regulation
• D. Transcription factor regulation -> RAF 1 -> MEK -> ERK

Answer: (A)