Question: What is the PCNA or nuclear cell proliferation antigen? 
 Options:  <1> It is a protein that prevents the double helix from forming in the replication bubble. <2> It is a protein that increases the ability to replicate long fragments of eukaryotic DNA polymerase. <3> It is the protein responsible for the elimination of positive superhelices. <4> It is the typical conformation of the DNA double helix in eukaryotes. <5> It is the enzyme responsible for copying the DNA of the telomeres.
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