DNA Replication

semi-conservative Mendelson and Stahl, 1958 each new DNA molecule consists of 1 parent (old) strand and one new strand 10 steps

Process 1) DNA helicase breaks H bonds between complementary base pairs 2) Strands are kept apart by single- stranded binding proteins 3) Copying occurs in 2 directions at once- toward fork on 3’ end, away from fork on 5’ end

Process 4) Replication occurs at many points at the same time. Replication bubbles form 5)RNA primers laid down by primase, used by DNA polymerase III as a starting point 6) nucleotides added to 3’ end, leading strand built towards fork

Process 7) lagging strand (Okazaki fragments), built discontinuously away from fork 8) DNA polymerase I removes RNA primers, replaces them with nucleotides 9) DNA ligase joins Okazaki fragments- phosphodiester bonds 10) DNA polymerase I and III proofread