The cuticle genes of drosophila: a developmentally regulated gene cluster.

A 36 kilobase (kb) DNA segment of the Drosophila genome that contains several larval cuticle protein genes has been cloned and characterized. This segment maps at chromosomal locus 44D. It contains five genes, all of which are expressed at the same time of Drosophila development. Four of the genes are clustered within 7.9 kb of DNA and are abundantly expressed as poly(A)RNA in the epidermis of late third instar larvae but are not abundantly expressed in other developmental stages. A fifth gene lies 8 kb away from this cluster and is expressed at a much lower level in late third instar larval poly(A) RNA. Three of the four abundantly expressed genes have been shown to code for larval cuticle proteins; less decisive evidence indicates that the fourth gene also probably codes for a larval cuticle protein. Some of the genes are related in DNA sequence, and the proteins encoded in the cluster are related immunologically. Thus the cuticle genes encoded by the segment at 44D are members of a family of genes of common ancestry, which share the same pattern of developmental expression and reside in a small segment of the Drosophila genome.