The properties of gene Dm 225, a representative of dispersed repetitive genes in Drosophila melanogaster.

The properties of Dm 225 DNA, a fragment of D.melanogaster genome 2.9 kb in length excised by EcoRI endonuclease and cloned in the lambda gt phage or pMB9 plasmid, are described. The DNA hybridizes to a significant portion (0.8%) of total polysomal poly(A)(+)RNA (mRNA). The size of the hybridizing mRNA is about 2.3 kb (19S); it is present in the fraction of heavy polysomes. Dm 225 DNA fragments obtained with the aid of Hae III endonuclease have been mapped. mRNA hybridizes with all the fragments. In one of the end fragments, the 3'-end of mRNA has been localized and thus the direction of transcription determined. About 250 copies of the gene Dm 225 are present in the haploid genome of D.melanogaster, and all of them have the same size upon restriction with EcoRI endonuclease. On the other hand, the sequences of the genome adjacent to Dm 225 DNA are different and may vary from one cell line to another as evidenced by experiments in which the D.melanogaster DNA was restricted by Hind III endonuclease. In combination with in situ hybridization data /1,2/ the results obtained in this paper demonstrate that the structural gene present in Dm 225 DNA is a representative of a multiple gene family dispersed throughout the whole genome of D.melanogaster.Images