Questions

The clotting of blood is a chain reaction initiated by the enzyme thrombokinase produced by the platelets. This causes prothrombin to be converted into thrombin in the presence of Ca++ion.

Thrombin combines with fibrinogen  to produce fibrin threads which entangles the corpuscles to form the clot.

If you were to produce a protein in bacterial cloning systems, you would not get the same post transcriptional and post translational modifications because the prokaryotic and eukaryotic systems work differently on the modifications.

Thus human recombinant protein genes are usually cloned in yeast cells. Also since they have a short generation time, they can be easily culture.