What was Griffith trying to learn when he set up this experiment?
While trying to find a cure for pneumonia, Griffith made a major scientific discovery. Griffith’s famous 1928 experiment showed us that bacteria can distinctly change their function (what they do) and form (how they look). Before his experiment, scientists believed that bacteria were fixed and unchangeable!
How did Griffith explain the transformation of R strain?
Griffith introduced heat-killed ‘S’- strain bacteria Streptococcus in to a mouse along with live ‘R’ strain bacteria. Some ‘transforming principle’ transferred from the heat-killed ‘S’ strain had enabled the ‘R’ strain to synthesise a smooth polysaccharide coat and become virulent.
How did Griffith determine which strain caused disease?
Griffith reasoned that some chemical factor that could change harmless bacteria into disease-causing bacteria was transferred from the heat-killed cells of the S strain into the live cells of the R strain. He called this process transformation, because one type of bacteria had been changed permanently into another.
What did Avery conclude caused transformation?
What did Avery conclude caused transformation? DNA was the transforming factor. The harmless bacteria would not have been transformed, and the mice would have lived.
What did Avery’s experiment prove?
In a very simple experiment, Oswald Avery’s group showed that DNA was the “transforming principle.” When isolated from one strain of bacteria, DNA was able to transform another strain and confer characteristics onto that second strain. DNA was carrying hereditary information.
Why did Griffith call the process he observed transformation?
Griffith called the process he observed transformation because the mouse had been transformed. the harmful bacteria had been transformed. the harmless bacteria had been transformed.
What did Hershey and Chase conclude?
Hershey and Chase concluded that protein was not genetic material, and that DNA was genetic material. Unlike Avery’s experiments on bacterial transformations, the Hershey-Chase experiments were more widely and immediately accepted among scientists.
Why did Hershey and Chase grow viruses in cultures?
Why did Hershey and Chase grow viruses in cultures that contained both radioactive phosphorus and radioactive sulfur? Hershey and Chase used both radioactive phosphorus and radioactive sulfur. This was a clever strategy since they knew that protein contained almost no phosphorus and DNA contains no sulfur.
Why did Hershey and Chase use 32P and 35S?
Discuss the rationale and conclusions of this experiment. The 32P (phosphorus) was used in the Hershey-Chase experiment because phosphorus is present in deoxyribonucleic acid (DNA), but not in protein. Hence, 35S was used to label only the proteins because DNA does not contain sulfur.
Why was s35 used in this experiment?
Why were phosphorus-32 and sulfur-35 perfect for what Hershey & Chase were investigating in their experiments? They were perfect because proteins contain almost no phosphorus and DNA contains no sulfur, so the radioactive isotopes would show up in the cells if the phosphorus-32 or sulfur-35 appeared.
How would Hershey and Chase learn whether genes were made of protein or DNA?
How would Hershey and Chase learn whether genes were made of protein or DNA? They would learn whether genes were made of protein or DNA by creating an experiment using phosphorus- 32 and sulfur- 35, as markers in their experiment. Concluded that the genetic material of the bacteriophage was DNA.
How did Hershey and Chase label phage DNA?
Method. Hershey and Chase used T2 phage, a bacteriophage. The phage infects a bacterium by attaching to it and injecting its genetic material into it. They labeled the phage DNA with radioactive Phosphorus-32.
How did Hershey and Chase use radioactivity to draw a conclusion about proteins and DNA?
Hershey and Chase studied bacteriophages which are viruses that attack bacteria. They labeled the bacteriophage with radioactive isotopes to see where it goes when a virus attacks. They discovered that nearly all the radioactivity was found in phosphorus, confirming that DNA contains genetic material, not protein.
What virus did Hershey and Chase start with?
In 1952, Alfred Hershey and Martha Chase published a convincing demonstration that DNA (not protein) was the genetic material. The Hershey–Chase experiment was carried out with a virus, called bacteriophage T2, that infects bacteria. Bacteriophage T2 consists of little more than a DNA core packed inside a protein coat.
How did Hershey and Chase know that it was the DNA that had infected the bacterial cells in their experiment?
Why did Hershey and Chase label the viral DNA with radioactive phosphorous and not radioactive sulfur? They labeled the DNA of a bacteriophage with radioactive phosphorus & found that after the bacteria were infected the radioactive phosphorus was in the bacteria.
What did Griffith conclude from his experiment?
Conclusion: Based on the observation, Griffith concluded that R strain bacteria had been transformed by S strain bacteria. The R strain inherited some ‘transforming principle’ from the heat-killed S strain bacteria which made them virulent. And he assumed this transforming principle as genetic material.
Which combination of bacteria killed the mice and showed that transformation occurred?
What did Avery conclude?
Because the ability to cause disease was inherited by the offspring of the transformed bacteria, he concluded that the transforming factor had to be a gene. In 1944, Oswald Avery tested the transforming ability of many substances. Only the DNA from the bacteriophage showed up in the infected bacterial cell.
What did Griffith conclude transformed the harmless bacteria in his experiment?
In Griffith’s experiment, he mixed heat-killed S-strain bacteria with live, harmless bacteria from the R-strain. When this mixture was injected into mice, the mice developed pneumonia, died. He was able to conclude that genes from the harmful bacteria transferred to the harmless bacteria, and transformed them.
What happened when Griffith injected mice with the harmless R-strain bacteria alone?
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What was Griffith’s hypothesis?
Through a series of experiments, Griffith established that the virulence of the S strain was destroyed by heating the bacteria. Based on these observations, Griffith hypothesized that a chemical component from the virulent S cells had somehow transformed the R cells into the more virulent S form (Griffith, 1928).
What did Hershey and Chase conclude was the genetic material of the virus?
Hershey and Chase concluded that DNA, not protein, was the genetic material. They determined that a protective protein coat was formed around the bacteriophage, but that the internal DNA is what conferred its ability to produce progeny inside a bacterium.
What enzyme makes it less likely that DNA will be lost from telomeres?
What did the experiments of Griffith and Avery show about genetic information?
The experiments of Griffin and Avery proved that DNA of heat-killed S strain bacteria was responsible for developing pneumonia in mouses that were infected with heat-killed S and live R strain bacteria. They concluded that DNA of the S strain bacteria was passed on the next generation, which was able to infect lungs.
What did the experiments that Frederick Griffith performed with R and S pneumonia bacteria and mice tell us about heredity in the cell?
However, when the dead S-strain bacteria were mixed with live R-strain bacteria and injected, the mice died. Griffith’s Experimental Results. Griffith showed that a substance could be transferred to harmless bacteria and make them deadly.
What are the 3 key roles of DNA?
What are the three key roles of DNA? Storing, copying, and transmitting information.