Also, going thru the mark scheme points:
-protein; it is a peptide hormone
-binds to receptors on; found on the cell surface membrane.. peptide hormones have polar groups and thus cant cross cell membrane directly
-(multipotent) stem cells; like i said above, about the Haemopoietic stem cells
-triggers a series of biochemical reactions inside the cell; this is the Protein Kinase Cascade ... signal transduction mechanism... we dont need to know about it...
-resulting in production of a substance that; it uses secondary messengers
-attaches to operator region/interacts with or acts as a transcription factor; self explanatory
-switches on genes; by binding to promoter and easily allowing the formation of the transcription initiation complex
-which trigger mitosis;
-or produce proteins which alter structure and or function of cells; like haemoglobin.... or enzymes that remove the nucleus (remember, red blood cells are enucleated)
-so they become specialised/differentiated