PAs write prescriptions and see patients independently but work registered with a MD or DO.
To become a PA one must complete a 4-year bachelor's degree along with specific prerequisite classes (much like medical school minus the physics pre-reqs), take the GRE, then apply to accredited Physician Assistant Programs.
After being invited to an interview and being accepted, PAs must complete 27-36 months of comprehensive medical training. Following graduation, they have to pass the PANCE boards (Physician Assistant National Certification Exam), apply for jobs, and then they are ready to work in any specialty with a physician.