The myc family of proto-oncogenes consists of at least three members, whose expression is tightly and co-ordinately regulated. The genes are nevertheless dispersed to three distinct chromosomal sites in humans. We have now used somatic cell genetics and the analysis of restriction fragment length polymorphisms (RFLPs) to identify and chromosomally map two mouse N-myc loci, to chromosomes 12 and 5, and two L-myc loci, provisionally to chromosomes 4 and 12. The second locus in each pair may be a pseudogene.
