You perform an in situ hybridization on Drosophila melanogaster embryos. You apply a probe labeled with a fluorescent stain that is complementary to mRNA transcripts of the gene hunchback. In early stages of embryogenesis you observe fluorescence for the entire anterior half of the embryo only. In embryos at a later stage of development you see the same pattern in the anterior, and also a stripe of fluorescence in the posterior half. What can you conclude about the expression of hunchback from this?