Frameshift mutants display altered assembly phenotypes. The wild-type (A, B) and the G-GP mutant (C, D) produce the normal intracytoplasmic immature particles (A, C) which can then be seen budding from the plasma membrane (B, D). Mutant G-GPP (E–H) also produced intracytoplasmic particles (E), but also an abundance of C-type-like assembling and budding structures at the plasma membrane (F–H). These structures were seen at various levels of completion with some appearing to continue assembling into the cytoplasm with visible plasma membrane support (G, black arrows). Mutant GP-GPP (I, J) produced only incomplete and aberrant intracytoplasmic structures (I); although the radius of curvature of these incomplete rings was similar to that of the wild-type immature particles. GP-GPP budding structures were also observed (J), some of which appeared C-type-like. The scale bars represent 100 nm.