“…Many studies have indicated that the DNA of mammalian cells is replicated in a specific temporal order (Bader et al, 1963;Braun and Wili 1969;Burke and Fangman, 1975;Kikuchi and Sandberg, 1964;Mueller and Kajiwara, 1966;Mukherjee et al, 1968;Taylor, 1960;Taylor et al, 1971). Furthermore, the period in S phase during which an individual gene is replicated appears to be identical and heritable from one cell generation to the next (Aebersold and Burki, 1976;Amaldi et al, 1969;Balazs et al, 1973;Giacomoni and Finkel, 1972;Hamper et al, 1974;Kasupski and Mukherjee, 1977;Kee and Haber, 1975;Orkin and Littlefield, 1971;Stambrook, 1974;Taylor, 1974).…”