Okazaki fragments

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During DNA replication the DNA duplex is unwound and two daughter strands are formed at the replication fork. DNA polymerase can only add nucleotides in the 5' to 3' direction, hence the synthesis of the one of the daughter strands, the leading strand, can proceed continuously in the same direction as movement of the replication fork.  
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During [[DNA replication|DNA replication]] the [[DNA|DNA]] duplex is unwound and two daughter strands are formed at the [[Replication fork|replication fork]]. [[DNA polymerase|DNA polymerase]] can only add [[Nucleotide|nucleotides]] in the 5' to 3' direction, hence the synthesis of the one of the daughter strands, the leading strand, can proceed continuously in the same direction as movement of the [[Replication_fork|replication fork]].  
  
However a complication arises&nbsp;with the replication of the other daughter strand, the lagging strand. As growth must occur in the 5'&nbsp;to 3' direction the copying of&nbsp;the template must somehow occur in the opposite direction as the movement of the replication fork. The cell accomplishes this by synthesising a new RNA primer every&nbsp;hundred bases&nbsp;or so as more of the strand is exposed.&nbsp;Each of these primers is elongated in the 5' to 3' direction forming&nbsp;segments&nbsp;called Okazaki fragments, named after their discoverer Reiji Okazaki. The RNA&nbsp;primer is&nbsp;then removed and the&nbsp;enzyme DNA ligase joins the adjacent fragments&nbsp;together.<ref>Pg. 146, Molecular Cell Biology, Harvey Lodish et al.</ref>
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However a complication arises&nbsp;with the replication of the other daughter strand, the lagging strand. As growth must occur in the 5'&nbsp;to 3' direction the copying of&nbsp;the template must somehow occur in the opposite direction as the movement of the replication fork. The cell accomplishes this by synthesising a new [[RNA|RNA]] primer every&nbsp;hundred bases&nbsp;or so as more of the strand is exposed.&nbsp;Each of these primers is elongated in the 5' to 3' direction forming&nbsp;segments&nbsp;called Okazaki fragments, named after their discoverer [[Reiji Okazaki|Reiji Okazaki]]. The RNA&nbsp;primer is&nbsp;then removed and the&nbsp;[[Enzyme|enzyme]] [[DNA ligase|DNA ligase]] joins the adjacent fragments&nbsp;together&nbsp;<ref name="null">Molecular Cell Biology, 7th Edtion, Harvey Lodish et al., Page: 146</ref>.
  
 
=== References  ===
 
=== References  ===
  
 
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Latest revision as of 08:50, 17 November 2014

During DNA replication the DNA duplex is unwound and two daughter strands are formed at the replication fork. DNA polymerase can only add nucleotides in the 5' to 3' direction, hence the synthesis of the one of the daughter strands, the leading strand, can proceed continuously in the same direction as movement of the replication fork.

However a complication arises with the replication of the other daughter strand, the lagging strand. As growth must occur in the 5' to 3' direction the copying of the template must somehow occur in the opposite direction as the movement of the replication fork. The cell accomplishes this by synthesising a new RNA primer every hundred bases or so as more of the strand is exposed. Each of these primers is elongated in the 5' to 3' direction forming segments called Okazaki fragments, named after their discoverer Reiji Okazaki. The RNA primer is then removed and the enzyme DNA ligase joins the adjacent fragments together [1].

References

  1. Molecular Cell Biology, 7th Edtion, Harvey Lodish et al., Page: 146
 
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