An attempt to approach the molecular mechanisms of primary sex determination: W‐ and Y‐chromosomal conserved simple repetitive DNA sequences and their differential expression in mRNA

The biological role of simple repetitive DNA consisting of short, tandemly arrayed sequences, is still enigmatic. Previously we have described how simple quadruplet repeats (sqr)isolated from a sex‐specific snake satellite ( Elaphe radiata ) are also “sex‐specifically” arranged in mouse and man (Epplen et al, '81, '82a). In the mouse, these sqr are interspersed on all chromosomes, but a substantial part is concentrated in the pericentromeric region of the Y‐chromosome (Epplen et al., '82b). In one of the subcloned snake satellite DNA component (pErs5), the sqr are adjacent to a single‐copy sequence that in turn identifies a male‐specific putative mRNA in the mouse (Epplen et al. '82b). The isolated stretch of sqr themselves cross‐hybridizes with at least two species of poly (A) + RNA from mice occurring in both sexes (Epplen et al., '82b, '83). By examining one of the non‐sex‐specific transcripts, we demonstrate here substantial open reading frames in the corresponding 2.5‐kilobase (kb)‐long mouse cDNA clone, including some 130 copies of sqr. The results are discussed in the context of mechanisms of primary sex‐determination in vertebrates, in particular the gonadal induction mechanism in heterogametic sex determination.