Figure 16-6: (A)  The packaging model.  The empty procapsid shows only binding sites for s.  After a full size s is packaged, the s sites disappear and m sites appear.  After a full size m is packaged, the m sites disappear and l sites appear.  After a full size l is packaged, minus strand synthesis commences.  After minus strand synthesis is completed, plus strand synthesis commences.  (B)  If segment s is of the size equal to the sum of both s and m, the s sites will disappear and the l sites will appear and segment l will be packaged without segment m.