Definition is a rhetorical mode that can be used in something smaller or shorter than a full paper. You can use extended definition for several paragraphs only in a paper of much greater length. You also can add to a paper a one-paragraph definition--like a brief encyclopedia definition.
The research group, headed by Dr. Lukas Sommer at the Swiss Federal Institute of Technology, has identified a heretofore unknown role for the TGF cell-to-cell signaling pathway in the pathogenesis of DiGeorge syndrome.
Using the FISH test for 22q11.2, it was discovered that about 95% of patients with DiGeorge syndrome and VCFS have a deletion. This special FISH test for 22q11.2 deletions is available in many clinical laboratories that look at chromosomes (referred to as cytogenetics laboratories).