Correct option is A
Explanation-
This is a classic Receptor Tyrosine Kinase (RTK) → Ras → MAPK/ERK signaling pathway, which is commonly involved in cell proliferation.
Step-wise Explanation of Each Component in the Pathway:
a - Grb2 (Growth factor receptor-bound protein 2) - Adaptor protein, binds phospho-RTK
b - SOS (Son of Sevenless) - Guanine nucleotide exchange factor (GEF) → converts Ras-GDP to Ras-GTP
c - Ras-GTP (Active Ras) - Small GTPase, triggers downstream MAP kinase cascade
d - ERK (Extracellular signal-regulated kinase) - MAP kinase → drives transcription and cell proliferation
Overall Sequence:
Ligand → RTK Activation
RTK recruits Grb2 (a).
Grb2 recruits SOS (b).
SOS activates Ras (GDP → GTP form) (c).
Activated Ras triggers MAPK/ERK cascade → ERK (d).
ERK enters nucleus and triggers genes for cell proliferation.
Final Answer:
Option a : a → Grb2, b → SOS, c → Ras-GTP, d → ERK
