Flash Cards 13.1 and 13
<p>Transformation</p>
<p>change in genotype and phenotype due to assimilation of external DNA by a cell</p>
<p>Think: Griffith and Avery</p>
<p>Griffith did not know in 1928 what the transforming factor was made of! </p>
<p>Avery and team figured it out. </p>
<p>phage</p>
<p>Virus that attacks bacteria</p>
<p>Chargaff's rules</p>
<p>DNA base composition varies between species</p>
<p>For each species. the % of A and T are roughly equal</p>
<p>The % of G and C bases are roughly equal. </p>
<p>photo 51</p>
<p>Confirmed DNA is a helix</p>
<p>2 strands (not 3)</p>
<p>uniform width (eliminating Watson's idea that A could pair with A)</p>
<p>Antiparallel</p>
<p>subunits run in opposite directions</p>
<p>5' to 3' paired to a strand that is running 3' to 5'</p>
<p>The 5' end has a phosphate group, the 3' a -OH</p>
<p></p>
<p>semiconservative model of replication</p>
<p>Proposed by Watson and Crick, proven by Meselson and Stahl.</p>
<p>origins of replication</p>
<p>sites where DNA replication begins</p>
<p>Replication fork</p>
<p>Y shaped region where the parental strands are being unwound by helicase (shown in yello)</p>
<p>single-strand binding proteins</p>
<p>bind to unpaired DNA strands to keep them from re-pairing</p>
<p>topoisomerase or gyrase</p>
<p>The untwisting of the DNA causes strain ahead of the fork.</p>
<p>Topoisomerase relieves the strain.</p>
<p>primer</p>
<p>short stretch of RNA (5 to 10 nucleotides long)</p>
<p>Made by primase. </p>
<p>The primer is shown in green. </p>
<p>DNA polymerase</p>
<p>catalyze the synthesis of new DNA by adding nucleotides to the 3' end of the preexisting chain. </p>
<p>There are several polymerases in <em>E.Coli</em> but 2 you need to know. </p>
<p>DNA polymerase I and DNA polymerase III</p>
<p>There are 11 in eukaryotes! </p>
<p>DNA polymerase can add 500 nucleotides per second in prokaryotes and 50 per second in human cells.</p>
<p>dATP or dGTP, etc</p>
<p>a sugar, base, and three phosphates. </p>
<p>2 phosphates are released when a nucleotide is added. </p>
<p>exergonic reaction/helps drive polymerization</p>
<p>leading strand vs. lagging strand</p>
<p>leading: one primer, made continuously by DNA pol III</p>
<p>lagging: many primers, made discontinuously, series of segments called Okasaki fragments.</p>
<p>Fragments are 1000-2000 nucleotides in <em>E. coli</em> and 100-200 nucleotides in Eukaryotes</p>
<p>ligase</p>
<p>enzymes the joins the sugar-phosphate backbones of the Okasaki Fragments</p>
<p>We'll see it again in figure 13.21 and 13.25</p>
<p>Anytime repairs must be made, ligase is used! </p>
