Transformation Experiment. Pneumococcus bacteria include two strains, a virulent S strain with a Smooth glycoprotein coat that kills mice (left), and a non-virulent R Rough strain that does not (middle). Heating destroys the virulence of S (right).

The disease causing strain grew into smooth colonies on culture plates where the harmless strain produced colonies with rough edges. The differences in appearance made the two strains easy to distinguish.

What result from Griffith’s experiment suggested that the cause of pneumonia was not a chemical poison released by the disease-causing bacteria? When he took a culture of these cells, heated the bacteria to kill them, and injected the heat-killed bacteria into mice; the mice survived.

Griffith’s experiment, reported in 1928 by Frederick Griffith, was the first experiment suggesting that bacteria are capable of transferring genetic information through a process known as transformation.

When heat-killed, disease-causing bacteria and harmless bacteria were injected together, the mice were killed.

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.

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.

In this experiments, Griffith injected mice in the lab with live R-type of bacteria. They did not suffer from the disease. He thus concluded that heat-killed smooth type bacterial caused a transformation of the living rough type bacteria. This experiment suggested that DNA and not proteins are the genetic material.

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).

In their experiments, Hershey and Chase showed that when bacteriophages, which are composed of DNA and protein, infect bacteria, their DNA enters the host bacterial cell, but most of their protein does not. Hershey and Chase and subsequent discoveries all served to prove that DNA is the hereditary material.

Griffith’s Experiment was an experiment done in 1928 by Frederick Griffith. It was one of the first experiments showing that bacteria can get DNA through a process called transformation. In this experiment, bacteria from the III-S strain were killed by heat, and their remains were added to II-R strain bacteria.

What did Avery conclude? He concluded that DNA transmits genetic information.

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.

Her evidence demonstrated that the two sugar-phosphate backbones lay on the outside of the molecule, confirmed Watson and Crick’s conjecture that the backbones formed a double helix, and revealed to Crick that they were antiparallel.

Hershey and Chase concluded that protein was not genetic material, and that DNA was genetic material.

Bacteriophages were used because they contain little more than DNA and protein. Alfred Hershey and Martha Chase used the bacteriophages because of their connection to DNA. In one batch, the phages (short for bacteriophages) were grown with radioactive phosphorous, which means it was incorporated into phage DNA.

Bacteriophages were used because they contain little more than DNA and protein. Hershey and Chase were able to isolate each factor to determine which was active.

What technique did Hershey and Chase use to study the viruses in their experiments? They used radioactive isotopes of phosphorus-32 and sulfur-35 as markers so they could trace the proteins and DNA to see what they were doing to the cell.

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.

Why did Hershey and Chase chose 32p and 35s for use in their 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.

What were the main criteria taken under consideration for the experiment by Hershey and Chase? Explanation: The two factors considered by Hershey and Chase were the simple composition of T2 bacteriophage, that is, DNA and protein. Thus radiolabelling of only one element was required.

Neither statement is true. Tm is NOT related to base composition. The more hydrogen bonds between bases, the higher the temperature needed to separate the pair.

Salt environment Divalent cations have the biggest impact on Tm—changes in the millimolar range are significant. Increasing the concentration of monovalent cations, such as Na+, up to 1–2 M stabilizes oligos. However, these higher concentrations can significantly impact Tm.

The Temperature of Melting (Tm) is defined as the temperature at which 50% of double stranded DNA is changed to single-standard DNA. The higher the melting temperature the greater the guanine-cytosine (GC) content of the DNA.

Heat double-stranded DNA (native DNA) It denatures or melts and becomes single-stranded. High pH facilitates the denaturation since it interferes with the base-pairing.

At pH 9 or higher, DNA is susceptible to alkaline denaturation due to the abundance of hydroxide ions. These negatively-charged ions remove hydrogen ions from the base pairs of DNA, thereby breaking the hydrogen bonds between and causing the DNA strands to denature.

At high pH, then, the solution is rich in hydroxide ions, and these negatively-charged ions can pull hydrogen ions off of molecules like the base pairs in DNA. This process disrupts the hydrogen bonding that holds the two DNA strands together, causing them to separate.

Extraction of DNA containing samples with acidic phenol results in the denaturation of the DNA, and once denatured, the DNA partitions to the organic phase. This is a key feature of many RNA purification protocols, which is one of the reasons acidic buffer-saturated phenol is used.