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.
T4 DNA ligase is an ATP-dependent ligase that catalyzes a joining reaction between DNA molecules. By joining the 3â-hydroxy and 5â-phosphate termini to form a phosphodiester, DNA ligases are absolutely essential for DNA replication and repair in all organisms.