A T C (Klug Cummings 1997) Levene's Tetranucleotide Hy pothesis Early experiments suggested that the four bases occur in DNA in equal ratios, possibly as a repeating tetramer. The implications was that the structure of DNA was too simple and too regular to contribute to hereditary variation: attention thereafter focussed on protein as the heredity substance
Levene's Tetranucleotide Hypothesis Early experiments suggested that the four bases occur in DNA in equal ratios, possibly as a repeating tetramer. The implications was that the structure of DNA was too simple and too regular to contribute to hereditary variation: attention thereafter focussed on protein as the heredity substance
Frederick Griffith In 1928 a scientist named frederick Griffith was working on a project that enabled others to point out that DNA was the molecule of inheritance. Griffiths experiment involved mice and two types of pneumonia, a virulent and a non-virulent kind. He injected the virulent pneumonia into a mouse and the mouse died. Next he injected the non-virulent pneumonia into a mouse and the mouse continued to live. After this, he heated up the virulent disease to kill it and then injected it into a mouse. The mouse lived on. Last he injected non-virulent pneumonia and virulent pneumonia, that had been heated and killed. into a mouse. This mouse died Why? Griffith thought that the killed virulent bacteria had passed on a characteristic to the non-virulent one to make it virulent. He thought that this characteristic was in the inheritance molecule. This passing on of the inheritance molecule was what he called transformation
Frederick Griffith In 1928 a scientist named Frederick Griffith was working on a project that enabled others to point out that DNA was the molecule of inheritance. Griffith's experiment involved mice and two types of pneumonia, a virulent and a non-virulent kind. He injected the virulent pneumonia into a mouse and the mouse died. Next he injected the non-virulent pneumonia into a mouse and the mouse continued to live. After this, he heated up the virulent disease to kill it and then injected it into a mouse. The mouse lived on. Last he injected non-virulent pneumonia and virulent pneumonia, that had been heated and killed, into a mouse. This mouse died. Why? Griffith thought that the killed virulent bacteria had passed on a characteristic to the non-virulent one to make it virulent. He thought that this characteristic was in the inheritance molecule. This passing on of the inheritance molecule was what he called transformation
Controls Living Ill (virulent) Living IIR t Heat-killed (avirulent) ⅢIS Inject Inject Inject Mouse dies Mouse lives Mouse lives ing IIR and Griffiths critical experiment eat-killed IlIS LivingⅢs Tissue recovered nect Mouse dies analyzed (Klug Cummings 1997) Griffith's Transformation Experiment Pneumococcus bacteria include two strains, a virulent IlIs strain with a Smooth coat that kills mice (left), and a non-virulent IIR Rough strain that does not (middle). Heating destroys the virulence of llIs (right). When heat-killed llIS is mixed with live IIR and injected into mice, the mouse dies, and its tissue contains living bacteria with smooth coats like Ils, and these bacteria are subsequently virulent to mice. Something in the heat-killed lls bacteria has transformed the biological and hereditary properties of the IIR bacteria
Griffith's Transformation Experiment Pneumococcus bacteria include two strains, a virulent IIIS strain with a Smooth coat that kills mice (left), and a non-virulent IIR Rough strain that does not (middle). Heating destroys the virulence of IIIS (right). When heat-killed IIIS is mixed with live IIR and injected into mice, the mouse dies, and its tissue contains living bacteria with smooth coats like IIIS, and these bacteria are subsequently virulent to mice. Something in the heat-killed IIIS bacteria has 'transformed' the biological and hereditary properties of the IIR bacteria
Oswald Avery Fourteen years later a scientist named Oswald Avery continued with Griffith's experiment to see what the nheritance molecule was. In this experiment he destroyed the lipids, ribonucleic acids, carbohydrates, and proteins of the virulent pneumonia. Transformation still occurred after this. Next he destroyed the deoxyribonucleic acid. Transformation did not occur. Avery had found the inheritance molecule, dNA
Oswald Avery Fourteen years later a scientist named Oswald Avery continued with Griffith’s experiment to see what the inheritance molecule was. In this experiment he destroyed the lipids, ribonucleic acids, carbohydrates, and proteins of the virulent pneumonia. Transformation still occurred after this. Next he destroyed the deoxyribonucleic acid. Transformation did not occur. Avery had found the inheritance molecule, DNA!
Klug Cummings 1997) Centrifuge Heat-kill Homogenize cells Recover IllS filtrate lIS cells spun to Extract carbohydrates, bottom of tube lipids, and proteins lIS cells in liquid culture medium Averys isolation of the"Transforming Principle Avery repeated Griffith 's experiment of combining heat-killed virulent IlIs bacteria with non-virulent IIR bacteria. In order to isolate the transforming substance, he fractionated the heat-killed llis cells and selectively removed carbohydrates and lipids, leaving behind proteins and nucleic acids
Avery's isolation of the "Transforming Principle" Avery repeated Griffith's experiment of combining heat-killed virulent IIIS bacteria with non-virulent IIR bacteria. In order to isolate the transforming substance, he fractionated the heat-killed IIIS cells and selectively removed carbohydrates and lipids, leaving behind proteins and nucleic acids