Replication by strand displacement

·        Replication can occur in various numbers of ways. One of which is strand displacement replication. This is a type of replication consists in the replication of just one ssDNA molecule from a DNA template.

·         DNA replication is a semi-conservative replication, due to the fact that two double stranded DNA (dsDNA) strand are formed from one dsDNA strand and these two “daughter” dsDNA possess one of the strands from the “mother” DSdna. In other words, in a cell possessing one mother dsDNA, the DNA strand present in the cell is 100% of the mother dsDNA, but after replication, of all the DNA strand in the cell, 50% of it will be from the mother dsDNA and after another replication the percentage of mother dsDNA strands is 25% and so on.

  

·         Strand displacement replication occurs do to the fact that DNA polymerase III not only catalyzes replication from ssDNA templates, but catalyzes as well a replication process in which a flapped strand of DNA is combined with a complementary DNA strand. In this replication type, there are three strands of DNA: strand 1, strand 2 and strand 3. Strands 2 and 3 are connected to each other and strand 1 is complementary to strand 3. Both strand 1 and 3 possess small complementary nucleotidic sequences that strand 2 does not. What happens is that these small nucleotidic sequences of strands 1 and 3 can combine. Since these sequences are small, their connection is easily achieved, but can be torn apart just as easily. When this connection lasts long enough, the first non-connected nucleotide of strand 1 can link itself to its complementary nucleotid in strand 3. This process removes the nucleotide of strand 2 that was linked in that spot. This process repeats itself until strand 1 displaces strand 2 from strand 3.