In living organisms, cells are frequently being replicated. In order for this to occur, the DNA

500 WordsApr 23, 20192 Pages
In living organisms, cells are frequently being replicated. In order for this to occur, the DNA must be replicated during the S phase of mitosis. This process is conducted by protein complexes which include DNA polymerases, helicase, primers, ligase and topoisomerase. Though the mechanism’s purpose is to accurately attach the corresponding nucleotides to the parent strand, there are often mistakes within the new strand of DNA. The result of any error, such as insertion, deletion, or matching two purines or two pyrimidines, as well as matching two of the same nucleotide, can lead to defects in the function of the cell. In order to correct this, there are a variety of mechanisms which check and fix any mistakes made during replication. One…show more content…
Proteins can be labeled and tracked as well. When the tagged proteins bind to the DNA, they are detected. Two sample proteins from yeast were used to study the response of DNA binding proteins to nucleosomes along DNA. Theses protein complexes are mlhs1-pms1 and msh2-msh6 (Gorman, Plys et al. 2010). Though both used in mismatch repair, the two complexes function differently. Msh2-msh6 mainly repairs single base pairs (Kunkel et al. 2005). In addition, it is also often used to initiate repair by binding to DNA. Mlh1-pms1, instead of repairing just a few bases pairs, repairs a much longer strand of up to sixteen nucleotides. Examination of DNA curtains and DNA binding protein complexes msh2-msh6 and mlhs1-pms1 determined that separate complexes react differently to nucleosomes (Gorman, Plys et al. 2010). Mhls1-pms1 complexes can find a way around nucleosomes while still remaining close to the DNA, likely due to a ring configuration. This movement is referred to as “hopping” or “stepping.” In contrast, msh2-msh6 complexes cannot move around nucleosomes. This suggests that the mechanism is closer to the backbone of the DNA and therefore cannot move past larger complexes. In conclusion, DNA binding proteins used for mismatch repair respond to nucleosomes along DNA in a variety of ways. The protein complexes ability or inability to move past the nucleosome depends on the configuration and movement of the complex itself. Complexes

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