DNA Replication
Describe what must happen to DNA in order for cells to divide
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New Strands of DNA are made by:
In this way, the genetic code is completely
preserved and copied exactly
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Helicase works in both directions to unwind DNA.
Replication Bubbles
Accessing the DNA
Topoisomerase works ahead of helicase to cleave
and unwind the stands of DNA. This process
relieves tension ahead of each replication fork.
Single-stranded DNA binding protein (SSB)
prevents the unwound DNA from coiling back up.
DNA Polymerase III is only able to grow from an already existing 3’ end of a nucleic acid. This means that
it can only work in ONE DIRECTION.
Indicate the direction of growth of the DNA daughter strand by labeling the 3’ and 5’ ends of the parent strand, the RNA
primer and the growing daughter DNA molecule.
RNA primer
growing daughter strand
DNA
Polymerase III
parent strand
Take notes on the diagram below of a replication fork to summarize the action of each of the ENZYMES
involved in DNA replication. Be sure to explain the differences between the leading and lagging strands.
Study the diagram below. From memory, sketch a replication fork with all of the enzymes and labels that
are relevant to DNA replication. Include the directionality of each strand. It would be wise to cover the
completed diagram as you draw.
Summary of the DNA Replication Process