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Position of regularly spaced single-stranded regions relative to 5-bromodeoxyuridine-sensitive sites in sea urchin morula DNA


5-BROMODEOXYURIDINE (BUdR) inhibits cell differentiation and embryogenesis and yet has little effect on cell division or metabolism1. When sea urchin embryos are grown in the presence of BUdR, pre-gastrula DNA accumulates as 30–60S duplex pieces2. We have now found that naturally occurring, regularly spaced, single-stranded regions in morula DNA3 are the sites at which BUdR-induced breakage occurs, resulting in production of these 30–60S low molecular weight DNA pieces. The DNA pieces from morulae grown in BUdR are approximately half the length of DNA molecules from control embryos grown in thymidine (TdR).

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CASE, S., BAKER, R. Position of regularly spaced single-stranded regions relative to 5-bromodeoxyuridine-sensitive sites in sea urchin morula DNA. Nature 253, 64–66 (1975).

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