Df(1)ct4b1 contains a breakpoint that falls in the dec-1 transcription unti near the beginning of the open reading frame of the fc177 transcript.
In dec-129/dec-1ct4b1 mutant egg chambers the endochorion appears as a continuous electron dense layer in close association with the inner chorionic layer. Electron dense aggregates are not observed in the underlying vitelline membrane. However aggregates are observed within the vitelline membrane near the base of the dorsal appendages. Clumped endochorionic material is also observed in the interior of the dorsal appendages.