Spermatids are as good as sperm at DNA replication. (A) Sperm and spermatids are separately incubated with egg extracts supplemented with biotin-dUTP. Subsequently, DNA fibers are isolated and subjected to molecular combing, which reveals replication on single DNA fibers. (B) Examples of DNA fibers after immunostaining procedure. Antibody staining against DNA reveals the total length of the fiber (green) and antibody staining against biotin reveals the replicated DNA (red). The bottom panels show representative examples of replication staining from sperm and from spermatids incubated in egg extracts. (C) Replication extent measured as the proportion of DNA that incorporated biotin-dUTP to the total fiber length. Results are from at least 125 independent DNA fibers (22,000 kb of DNA for each sample). Error bars: SEM. Samples were not significantly different (P-value = 0.41, KS-test).
