DNA Replication
Molecular Diagnostics
(MDx) Review 534
STEP EXPLANATION
Strand separation
Synthesis of primers
Extension of primers
Removal of primers
Replacement of primers
Joining of Okazaki fragments
Helicase unwinds section of dsDNA to form replication forks. Both original strands of DNA will serve as
templates. Replication will proceed simultaneously on both strands, in opposite directions.
Primase reads section of code on DNA, attaches complementary nucleotides to form RNA primer that
provides 3’OH end needed to grow nucleotide chain.
DNA polymerase reads template, attaches complementary nucleotides starting at 3’ OH of primer. Code
is read in 3’ to 5’ direction. Synthesis on 3’–5’ template is continuous, forming leading strand. Synthesis
on 5’–3’ template is discontinuous, forming lagging strand of disconnected Okazaki fragments.
RNase H removes RNA primers.
DNA polymerase places nucleotides where primers used to be.
DNA ligase joins DNA fragments together.
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