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Where does replication begin?What happens here and how?
replication origin. the helix has become unwound in a small region. In theelectron microscope these look like ‘bubbles’ in the DNA. This process requires energy and is performed byenzymes called helicases. In the exposed single-stranded regions, new DNA can be synthesized
Each replication origin consists of _____ .
two replication forksmoving in opposite directions.
What is DNA polymerase and what does it do? What does it require?
The enzyme that directs new synthesis of DNA is calledDNA polymerase. DNA polymerase provides anenvironment in which the correctnitrogenous base can be aired with the next base in the template.This enzyme requires a template, a free3’OH, and deoxyribonucleoside triphosphates (dNTPs)
WHat does a primer do and how is it synthesized?
afree 3’OH is provided by a primer that is actually made ofRNA. This primer is synthesized by a specialized RNApolymerase called a primase, which can incorporate newribonucleotides without a pre-existing 3’OH.
What drives the reaction between the 3’OH on the ribose sugar and thephosphate group joined to the 5’carbon on the incoming nucleotide?
The energy of hydrolysis of thepyrophosphate (PPi) drives thereaction.
memorize this (flip)
Which is the leading strand? which is the lagging? Where is synthesis continuous?
leading is on the 5'-3' end of the DNA. The leading strand is thus created from the DNAs 3' end to the 5'. The lagging is the exact opposite. Synthesis is continuous on the leading strand
Why is synthesis not continuous in the lagging strand?
not continuous becauseof the need to polymerize in the 5’ to 3’ direction so a new single strandeed DNA is exposed and new primers must be made.
What are okazaki fragments?
The regions representingRNA primers and new DNA, with gaps.
What is the final step? This final step is catalyzed by______ and requires energy from ______.
The final step is replacing the RNA primers with DNA.DNA ligase, ATP
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