B11111

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    <td height="39" colspan="2" bgcolor="#03438A"><div align="center"><span class="STYLE25" style="margin-bottom: 0">Background</span></div></td>
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    <td height="88" colspan="2" bgcolor="#03438A" class="STYLE9"><p><span class="STYLE5"><strong>Site-specific recombination</strong><br />
      Site-specific  recombination differs from general recombination in that short specific  sequences which are required for the recombination, are the only sites at which  recombination occurs. These reactions invariably require specialized proteins  to recognize these sites and to catalyze the recombination reaction at these  sites.</span></p></td>
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    <td width="510" bgcolor="#03438A" class="STYLE9"><p class="STYLE5"><span class="STYLE10"><strong>Inverted  repeats</strong> <br />
      If the two sites  at which recombination will take place are oriented oppositely to one another  in the same DNA module then the following illustrates the sequence of events  that will take place:</span></p></td>
    <td width="444" bgcolor="#03438A" class="STYLE9"><p class="STYLE5"><span class="STYLE10"><strong>Direct repeats</strong> <br />
      While if oriented in the same direction, then the following illustrates the sequence of events:</span></p></td>
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    <td bgcolor="#03438A"><a href="http://www.mun.ca/biochem/courses/3107/images/rec_invert.GIF" target="_blank"><img src="https://static.igem.org/mediawiki/2008/1/1c/机理1.gif" width="364" height="350" border="0" align="left" /></a></td>
    <td bgcolor="#03438A"><a href="http://www.mun.ca/biochem/courses/3107/images/rec_direct.GIF" target="_blank"><img src="https://static.igem.org/mediawiki/2008/3/32/%E6%9C%BA%E7%90%862.gif" width="350" height="350" /></a></td>
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    <td height="118" bgcolor="#03438A" class="STYLE9"><p class="STYLE11">The net result is that <strong>the segment of  DNA between the two recombinogenic sites has inverted</strong> with respect to the  rest of the DNA module.<br />
      In other words, <strong><u>recombination at  inverted repeats causes an inversion</u></strong></p></td>
    <td bgcolor="#03438A" class="STYLE9"><p class="STYLE11">The net result is that <strong>the segment of  DNA between the two recombinogenic sites has been deleted</strong> from the rest of  the DNA module and appears as a circular module.<br />
      In other words, <strong><u>recombination at  direct repeats causes a deletion</u></strong>.</p></td>
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    <td height="54" colspan="2" bgcolor="#03438A" class="STYLE9"><p class="STYLE5"><span class="STYLE10"><strong>Note</strong> that the reverse reaction -- the recombination of a  circular module with another DNA module (either circular or linear), brings  about a fusion of both modules or the integration of one module into the  other. The integrated segment will be flanked by directly repeating sequences  which can, of course, be used to excise the integrated segment again.</span></p></td>
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    <td height="53" colspan="2" bgcolor="#03438A"><span class="STYLE7"><strong>Integration of bacteriophage lambda</strong></span></td>
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    <td height="54" colspan="2" bgcolor="#03438A"><p class="STYLE11"> <span class="STYLE9">In order for the lambda prophage to exist  in a host <em>E.&nbsp;coli</em> cell, it must integrate into the host chromosome  which it does by means of a <strong>site-specific recombination reaction</strong>. </span><br />
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    <td height="55" bgcolor="#03438A"><img src="https://static.igem.org/mediawiki/2008/3/30/消费税.jpg" width="510" height="320" /></td>
    <td height="55" bgcolor="#03438A"><p class="STYLE15">The <em>E.&nbsp;coli</em> chromosome contains  one <strong>attachment site</strong> which is designated <strong><em>attB</em></strong>. The site is  only 30 bp in size and contains a conserved central 15 bp region where the  recombination reaction will take place. The structure of the recombination site  is usually represented as <strong>BOB'</strong>.</p>
        <p class="STYLE15">The bacteriophage recombination site - <strong><em>attP</em></strong> - contains the  identical central 15 bp region as <strong><em>attB</em></strong>. The overall structure can  be represented as <strong>POP'</strong>.</p>
      <p class="STYLE15">Integration of bacteriophage lambda  requires one phage-encoded protein - <strong>INT</strong>, which is the <strong>integrase</strong> - and one bacterial protein - <strong>IHF</strong>, which is <strong>Integration</strong> <strong>Host</strong> <strong>Factor</strong>. Both of these proteins bind to sites on the <strong>P</strong> and <strong>P'</strong> arms of <strong><em>attP</em></strong> to form a complex in which the central conserved 15  bp elements of <strong><em>attP</em></strong> and <strong><em>attB</em></strong> are properly aligned. </p></td>
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        <td width="42%"><p align="center"><a href="http://www.mun.ca/biochem/courses/3107/images/POP_BOB.jpg"></a><img src="https://static.igem.org/mediawiki/2008/d/d9/Qweerw.jpg" width="500" height="110" /></p></td>
        <td width="58%"><p align="center"><a href="http://www.mun.ca/biochem/courses/3107/images/BOP_POB.jpg"></a><img src="https://static.igem.org/mediawiki/2008/6/63/Y.jpg" width="454" height="110" /></p></td>
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    <p>&nbsp;</p>
    <p>&nbsp;</p>
    <p>&nbsp;</p>
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        <td height="23" colspan="2" bgcolor="#03438A" class="STYLE24"><p class="STYLE4"><span class="STYLE11 STYLE4 STYLE23 STYLE5">The result of  recombination is that the integrated prophage is flanked by two attachment  sites but now they are slightly different: <em>attL</em> has the structure BOP' and <em>attR</em> has the structure POB'. </span></p>
            <p class="STYLE4">Cre-Lox  recombination is a special  type of site-specific recombination, which is often applied as a gene knockout  tool. <br />
              Cre is a site-specific  DNA recombinase, which can catalyse the recombination of DNA between specific  sites, e.g. loxP in a DNA module. When cells that have loxP sites in  their genome express Cre, a reciprocal recombination event will occur between  the loxP sites. The double stranded DNA is cut at both loxP sites  by the Cre protein. The strands are then rejoined with DNA ligase. The efficiency of recombination  depends on the orientation of the loxP sites. For two lox sites on the  same chromosome arm, inverted loxP sites will cause an inversion, while  a direct repeat of loxP sites will cause a deletion event.</p>
          <p class="STYLE4"> Lox P site<br />
            Lox P (locus of X-over P1) is  a site on the Bacteriophage P1 consisting of 34 bp. There exists an asymmetric  8 bp sequence in between with two sets of palindromic, 13 bp sequences flanking  it. The detailed structure is given below.</p></td>
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        <td height="11" colspan="2" bgcolor="#03438A" class=" STYLE13"><p><span class="STYLE2">aaaaaa</span><img src="https://static.igem.org/mediawiki/2008/6/6e/09875.jpg" width="803" height="104" align="middle" /></p>
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        <td height="12" colspan="2" bgcolor="#03438A" class=" STYLE13"><p align="right"><span class="STYLE26">back to</span> <a href="https://2008.igem.org/Project">Project</a> <span class="STYLE26">or</span> <a href="https://2008.igem.org/Team:Tianjin">Home</a> </p>
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