The defective chorion-1 gene (dec-1) in Drosophila encodes follicle cell proteins necessary for proper eggshell assembly. Multiple products of the dec-1 gene are formed by alternative RNA splicing and proteolytic processing [1]. Cleavage products include S80 (80 kDa) which is incorporated into the eggshell, and further proteolysis of S80 gives S60 (60 kDa). This repeat is usually found in 12 copies in the central region of the protein. Its function is unknown. Length polymorphisms of Dec-1 have been observed in wild-type strains, and are caused by changes in the numbers of the first five repeats [2].

1: Multiple proteins are produced from the dec-1 eggshell gene in Drosophila by alternative RNA splicing and proteolytic cleavage events. Waring GL, Hawley RJ, Schoenfeld T; Dev Biol 1990;142:1-12. PMID:1699826

2: Evolution of the dec-1 eggshell locus in Drosophila. II. Intraspecific DNA sequence analysis reveals length mutations in a repetitive region in D. melanogaster. Andersson S, Lambertsson A; J Mol Evol 1993;36:536-544. PMID:8350348