Bridge to the New World How and when humans first came to the Americas has long been a topic of intense debate. Theories to explain the colonization of the New Worldâthe last great habitable landmass to be occupied by humansâfocus on the Bering land bridge, or Beringia, which emerged between Siberia and Alaska during the last ice age.
DNA ligase I: ligates the nascent DNA of the lagging strand after the Ribonuclease H has removed the RNA primer from the Okazaki fragments. DNA ligase III: complexes with DNA repair protein XRCC1 to aid in sealing DNA during the process of nucleotide excision repair and recombinant fragments.
DNA Replication - synchronization of leading and lagging strands. DNA is replicated by continuous synthesis of a leading strand and discontinous synthesis of a lagging strand. Coordination between leading and lagging strand synthesis is achieved by the dimerization of DNA polymerase molecules at the replication fork. The DN A polymerase dimer moves with the replication fork. the polymerase at the leading strand template remains attached to the DNA, synthesizing the leading strand continuously. The lagging strand polymerase initiates DNA synthesis at the fork, from an RNA primer made by a primase complex.