"Looks like they're running out of fresh Jango.'" - Fi Skirata noting newer clones.
Clone Troopers are the soldiers of the Grand Army of the Republic during the Clone Wars. The obedient men are a genetic clones of the bounty hunter, Jango Fett. Towards the fall of the Jedi Order, the clones were less like Jango, as well as the earlier clones. The clones who had survived most of the war made up the 501st.
Troopers appear most often during the Genosis campaign, as well as on the RAS Prosecutor. In the case of the former, the clones appear to be actively holding the line or advancing whilst taking heavy casualties. On the Prosecutor, Trandoshans inflict heavy casualties on the remaining clone troopers, though a select few manage to effectively fight back. It's possible for Delta 38 to save some of the troopers in both cases. The troopers will fight enemy forces and attempt to secure the immediate area, but will not follow Delta Squad, and fall quickly when faced with superior opposition, or when outnumbered.