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Li_Karen_Block 2_MM10 (DNA Replication (Prokaryotes (13 mer - an AT-rich…
Li_Karen_Block 2_MM10
DNA Replication
Elongation - a new DNA strand being replicated by using the previous strand as a template, starting from the location of the primer. Okazaki fragments are then created by the lagging strand being unwinded. The fragments end in an RNA primer that is then removed, allowing the fragments to be joined together, creating an elongated strand
Termination -the last primer sequence, or the telomere section, must be removed from the lagging strand by an enzyme, creating shorter strands at the end of the process. After, nuclease enzymes removes any mismatched bases, and then DNA polymerase repairs the removed areas
Stalling of a strand is regulated by a protein called Tus, which recognizes and binds to 10 different terminator sites (ter sites) on the template DNA
Initiation - initiator proteins binding to the oriC, triggering unwinding by helicases. Topoisomerase proteins stay close to the unwinding strands to help relax the strain and prevent the DNA from being damaged. Then, primers, or short RNA sequences, are created to prepare for elongation
Oscillation - an important type of cell signaling characterized by the periodic change of the system in time
Semiconservative - each of the sister chromatids of the metaphase chromosome has one strand derived from the parent G1 chromosome (blue) and one new strand (red).
Bidirectional - replication bubble expands as the growing fork unzips the DNA and new strands are copied in 3’ direction. The parent strands serve as templates for making the complementary daughter strands
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Leading & Lagging Strand
Lagging : begins at the ori and is assembled with successive Okazaki fragments, growing in the 5’ direction rather than the polymerization direction of 5’ to 3’
Leading : begins at the ori with the RNA primer and elongates without breaking in the 3’ direction (downstream of the ori) until it reaches the end of the DNA molecule
Okazaki fragments -short sequences of DNA nucleotides used for replicating the rest of the DNA that is upstream of the ori.
Enzymes
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Primase - adds RNA primer to the parent template strand so that DNA Pol III can polymerize the complementary daughter strand in the 3’ direction
Helicase - unwinds and unzips the DNA double-helix and the single-stranded-binding (Ssb) protein binds to the single strands to keep them from reannealing
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