Size Distribution and Molecular Polarity of Newly Replicated DNA in Escherichia coli
AUTOR(ES)
Louarn, Jean-Michel
RESUMO
Newly synthesized DNA, in E. coli lysogenic for the phage λ, was labeled by short pulses of [3H]-thymidine, isolated, and separated on the basis of size by alkaline sucrose density gradient centrifugation. The molecular polarity of this DNA was determined by hybridization with each of the separated strands of λ DNA. The results show that, in the 3′ to 5′ direction, replication proceeds by synthesis of short chains that are subsequently joined to long DNA. This is true for both a polA+ and a polA- strain. (The polA locus codes for DNA polymerase I.) In the 5′ to 3′ direction, replication proceeds continuously, by addition of nucleotides to long DNA, for the polA+ strain. In the polA- strain, however, replication in the 5′ to 3′ direction is also discontinuous, but the discontinuities are 1-40 times less frequent than in the other direction.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=387997Documentos Relacionados
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