biology-class-12-unit-06-chapter-04-genetics-and-evolution-molecular-basis-of-inheritance-l-4-12-a85lm20rcag

<h3 id="successfeatures-of-genetic-materialsuccess"><Success>Features of genetic material</Success></h3>
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<ul>
<li>Contain complex information</li>
<li>Replicate faithfully</li>
<li>Encode phenotype</li>
<li>Capable of change. Without change, organisms would be incapable of variation and adaptation, and evolution could not occur</li>
</ul>
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<h3 id="successgriffiths-experimentsuccess"><Success>Griffith’s experiment</Success></h3>
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<ul>
<li>Reported in 1928</li>
<li>He was working on bacterium that causes pneumonia, <em>Streptococcus pneumonia</em></li>
<li>Griffith used two strains of pneumococcus bacteria, type III-S and type II-R</li>
</ul>
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<h3 id="successgriffiths-experiment-on-ratsuccess"><Success>Griffith’s experiment on rat</Success></h3>
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<ul>
<li>
<p>Injected type IIR bacteria into mice, the mice lived, and no bacteria were observed in blood</p>
</li>
<li>
<p>Injected type IIIS bacteria into mice, caused the mice to develop pneumonia and die, and bacteria were recovered from their blood</p>
</li>
</ul>
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<h3 id="successgriffiths-experiment-on-ratsuccess-1"><Success>Griffith’s experiment on rat</Success></h3>
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<ul>
<li>
<p>Injected large amounts of heat-killed type IIIS bacteria into mice, the mice lived and no type IIIS bacteria were recovered from their blood</p>
</li>
<li>
<p>Injected mice with a small amount of living type IIR bacteria, along with a large amount of heat-killed type IIIS bacteria the mice became infected with pneumonia and died, examined blood from the hearts of these mice, he observed live type IIIS bacteria</p>
</li>
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<h3 id="successavery-macleod-and-mccarty-experimentsuccess-1"><Success>Avery, MacLeod, and McCarty experiment</Success></h3>
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<ul>
<li>Finally added Dnase enzymes, capable of destroying DNA, in the filtrate</li>
<li>They poured the extract in culture of type IIR bacteria</li>
<li>Found the colonies of only IIR bacteria</li>
<li>There was no any IIIS bacteria developed in the culture</li>
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<h3 id="successconclusion-of-experimentsuccess"><Success>Conclusion of experiment</Success></h3>
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<ul>
<li>Enzymes such as trypsin and chymotrypsin, known to break down proteins, had no effect on the transforming substance</li>
<li>Ribonuclease, an enzyme that destroys RNA, also had no effect Enzymes capable of destroying DNA, however, eliminated the biological activity of the transforming substance</li>
<li><strong>Avery,</strong> MacLeod, and McCarty showed that purified transforming substance precipitated at about the same rate as purified DNA and that it absorbed ultraviolet light at the same wavelengths as does DNA</li>
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<h3 id="successwhy-radioactive-phosphorus-and-sulfursuccess"><Success>Why radioactive phosphorus and sulfur?</Success></h3>
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<li>
<p>To Know the fate of protein and DNA, they used radioactive forms (isotopes) of phosphorus and sulfur</p>
</li>
<li>
<p>A radioactive isotope can be used as a tracer to identify the location of a specific molecule, because any molecule containing the isotope will be radioactive and therefore easily detected</p>
</li>
<li>
<p>DNA contains phosphorus but not sulfur, so Hershey and Chase used 32P to follow phage DNA during reproduction</p>
</li>
<li>
<p>Protein contains sulfur but not phosphorus: so they used 35S to follow the protein</p>
</li>
</ul>
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<h3 id="successhershey-chase-experimentsuccess"><Success>Hershey-Chase experiment</Success></h3>
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<ul>
<li>
<p>First, Hershey and Chase grew E. coli in a medium containing 32P and infected the bacteria with T2 so that all the new phages would have DNA labeled with 32P</p>
</li>
<li>
<p><strong>They grew a second batch of E. coli in a</strong> medium containing 35S and infected these bacteria with T2 so that all these new phages would have protein labeled with 35S</p>
</li>
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<h3 id="successconclusionsuccess-1"><Success>Conclusion</Success></h3>
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<p>These results confirmed that DNA is the genetic material</p>
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<h3 id="successgriffiths-experimentsuccess-1"><Success>Griffith’s experiment</Success></h3>
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<p>$ \text {II R}  $ - Non Virulent - $ \text {II R}  $<br>
$ \text {III S}  $ - Virulent - $ \text {III S}  $</p>
<ol>
<li>
<p>$ \text {II R} \longrightarrow $ mice $ \longrightarrow $ mice live</p>
</li>
<li>
<p>$ \text {III S} \longrightarrow $ mice $ \longrightarrow $ mice dead</p>
</li>
<li>
<p>Heat killed $ \text {III S} \longrightarrow $ mice $ \longrightarrow $ mice live</p>
</li>
<li>
<p>$ \text {II R}  $ + HK $ \text {III S} \longrightarrow $ mice $ \longrightarrow $ mice dead</p>
</li>
</ol>
<p>Chemical $ \Rightarrow $ <strong><ins>Transforming Principle</ins></strong></p>
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