One gap junction consists of a cluster of closely packed pairs of transmembrane channels, the connexons, through which materials of low MW diffuse from one cell to a neighboring cell. A connexon is composed of a hexamer of connexins. Resides primarily in the ovary, oocytes and early embryos. It is a maternal protein that disappears by the late gastrula stage. Belongs to the connexin family. Alpha-type (group II) subfamily.