As a first step in analyzing the function of a cdc25 homolog during th
e embryonic development of Patella vulgata (P upsilon), genomic clones
encoding these stringlike proteins (Stl) were isolated and characteri
zed. These clones belong to four groups which are derived from differe
nt regions of the P upsilon genome. As the sequences of Stl genes from
two of these groups are almost identical, we suggest that these genes
represent copies of the same gene. The Stl3 gene, which has been anal
yzed in detail, consists of four exons separated by three introns. Its
sequence encodes a 250-amino-acid protein with a calculated weight of
28 kDa. The Stl protein contains regions conserved in all other cdc25
proteins. Stl messengers are not stored maternally in P upsilon oocyt
es and Stl transcription only starts after the first embryonic cleavag
es.