Two structurally different genes produce the same secreted human placental lactogen hormone.

Experiments were designed to determine if the members of the human placental lactogen (hPL) cluster, consisting of four nonallelic genes, are transcribed in term placenta. Taking advantage of differences in restriction endonuclease sites in the coding portions of the different hPL genes and thus of their putative cDNAs, we have identified two transcriptionally active nonallelic hPL genes in term placenta. The two expressed genes, which code for secreted hPL with identical amino acid sequences, are about equally represented in the hPL mRNA population.