structure and transcriptional pattern. This homeo‐box is part of a gene which is specifically
regulated during mouse prenatal development and expressed in a restricted number of
teratocarcinoma tumours as well as in adult testis. Hox1‐3 is shown to be a member of a
cluster of at least four homeo‐boxes lying within a 75‐kb segment of DNA on mouse
chromosome 6. The structure of the whole cluster, the Hox‐1 locus is presented.