DNA Replication in T7 DNA ligase acts GA BC D E F G GAB'CDE′FG Pairing of unreplicated terminal repeats GA B C D E F G GAB′ C D E F G Joining of new and old molecules by DNA ligase, forming a concatamer
DNA Replication in T7
DNA Replication in t7 BCDEFGABCDEF+GABcD T has a much B DNA polymerase more complex GG AA replication Cutting cc cIC enzyme DID DID scheme than EIE G DNA that seen for the other bacterial Cutting enzyme DNA polymerase Mature T7 (arrows) makes completes the molecule viruses single-stranded with terminal cuts cuts
DNA Replication in T7 T7 has a much more complex replication scheme than that seen for the other bacterial viruses
Large double-Stranded DNA bacteriophages the T-even Phages T2, t4 and t6 T4(as example) 1.7X 105 base pairs Have a unique base, 5-hydroxymethylcytosine instead of cytosine The above hydroxyl group is modified by addition of glucosyl residues This glucosylated dna is resistant to virtually all restriction endonucleases of the host
Large Double-Stranded DNA bacteriophages: the T-even Phages T2, T4 and T6 T4 (as example) – 1.7 X 105 base pairs – Have a unique base, 5-hydroxymethylcytosine instead of cytosine – The above hydroxyl group is modified by addition of glucosyl residues – This glucosylated DNA is resistant to virtually all restriction endonucleases of the host
DNA replication in T4 O0 Ta. Nucleases DNA polymerase Phage head and tail fiber Mature phage partice New sigma factors T4 lysozyme Phage DNA replication Ea arly mRNA Middle mRNA Late mRNA Set assembly Lysis Minutes Time course of events in phage t4 infection
DNA replication in T4 Time course of events in phage T4 infection
Enzyme DNA Replication in T4 GABcDEFGABcDEFGABcDEFGABcDEFGAB BcDEFGABcDEFGABcDEFGABcDEFG The cutting enzyme which forms virus sized fragments does not recognize specifIc locations on the long molecule. but cuts off DNA irrespective of the sequence Thus each viruS dNa sequences at the end of Long DNA Molecules different molecules are molecules attacked b different cutting
DNA Replication in T4 The cutting enzyme which forms virussized fragments does not recognize specific locations on the long molecule, but cuts off DNA irrespective of the sequence. Thus, each virus DNA sequences at the end of different molecules are different