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Eukaryotic Linear DNA Synthesis: Mechanism Of Telomere Addition

Eukaryotic Linear DNA Synthesis: Mechanism Of Telomere Addition. Note: The 3’ end of the chromosome will always be longer, but now all sequences in the chromosome will be replicated. Courtesy: Alberts et. al. Molecular Biology of the Cell.

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Eukaryotic Linear DNA Synthesis: Mechanism Of Telomere Addition

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  1. Eukaryotic Linear DNA Synthesis: Mechanism Of Telomere Addition Note: The 3’ end of the chromosome will always be longer, but now all sequences in the chromosome will be replicated Courtesy: Alberts et. al. Molecular Biology of the Cell

  2. Rolling circle replication is used to replicate some plasmids Plasmids are small circular DNA molecules that are double stranded For rolling circle replication, the outer strand is considered the (+) strand and the inner strand is the (-) strand To start rolling circle replication, the (+) strand is nicked (cut) In rolling circle replication, the (+) strand serves as a template for the (-) strand and the (-) strand serves as a template to make the (+) strand Prokaryotic DNA Replication: Rolling Circle Replication

  3. The nick in the (+) strand will create a free 3’ OH and allow for synthesis of a new (+) strand Synthesis of a new (+) strand will start at the free 3’OH using the (-) strand as a template Synthesis of a new (+) strand is continuous lending the name rolling circle because we go around the circle Synthesis of a new (-) strand uses the (+) strand as a template Synthesis of a new (-) strand occurs in a discontinuous replication Prokaryotic DNA Replication:RollingCircle Replication

  4. Prokaryotic DNA Replication: Evidence For Bi-Directional Replication In Bacteria • Although there are two replication forks created, there are two possible ways that the circular Bacterial chromosome could be replicated • Uni-directional (DNA is replicated at only one of the forks) • Bi-Directional (DNA is replicated at both forks) • Elizabeth Gyurasits and R.B. Wake showed that DNA replication in B. subtilis is bi-directional • Grew B. subtilisin the presence of 3H-Thymidine (weak radioactivity) for a short time • Then switch the B. subtilisto media with a more strongly radiolabelednucleotide (32P) • Exposed the replicating DNA to autoradiography • Both forks picked up the strongly radiolabeled nucleotide, and must have been replicating at the point where the shift occured

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