Bipolar birthdating in the rat retina in vivo using retroviral lineage analysis. Bipolar cells in clones from pEly control virus infections that contained one or two cells (usually rod-bipolar or bipolar-only clones) were scored. Bipolar cells in these clones were interpreted to be born on the day of infection. The percentage of cone bipolar cells and rod bipolar cells interpreted to be born on P0, P4 and P6 are shown. Retinas were infected on the indicated day. For P0, six retinas were used. For P4, three retinas were used. For P6, two retinas were used. A total of 200 clones were scored for each time point.