6.2: Relpication Flashcards
What direction is DNA synthesized? What direction does DNA Polymerase read the DNA template?
DNA is synthesized from the 5’ end (phosphate terminus) to the 3’ end (hydroxyl terminus). It is read from the 3’ end to the 5’ end.
What is the function of helicase?
Unwinds the DNA strands (splits two DNA strands apart)
What is the function of topoisomerase?
Relaxes the coil right before the helicase arrives at the replication fork.
What is the function of DNA polymerase?
It synthesizes new strands along the DNA template and builds 5’ to 3’. (Note that to build the strand this way, the polymerase attaches to the 3’end of the template strand.
What is the function of RNA primers and primase?
Primase joins nucleotides in order to make a primer. The primer binds to its complementary bases on the 3’ end of the template strand.
Why are RNA primers required for DNA replication?
You need them in order to start building the chain of nucleotides. This provides the first connection to the template strand.
How does the leading and the lagging strand differ?
They both are synthesized from the 5’ to 3´, but the lagging strand needs to reattach itself every so often in order to continue to build.
What is the function of DNA ligase?
It joins the DNA fragments on the lagging strand.
Describe the process of DNA replication using the enzymes described above (helicase, topoisomerase, DNA
polymerase, primase, RNA primers, and DNA ligase)
The helicase unwinds and breaks apart nucleotides at the replication fork. Right after, topoisomerase unwinds the following nucleotides. The primase then makes primers to attach to the 3’end of the DNA template strand. Then, the DNA polymerase begins to form a new strand of nucleotides from 5’to 3 On the lagging strand, ligase is used in order to connect the fragments of the new DNA strand.
