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 was transformed in Griffith’s experiment?
Griffith concluded that the type II-R had been “transformed” into the lethal III-S strain by a “transforming principle” that was somehow part of the dead III-S strain bacteria Today, we know that the “transforming principle” Griffith observed was the DNA of the III-s strain bacteria
What was the main outcome of Griffith’s experiments?
Griffith concluded that the heat-killed bacteria somehow converted live avirulent cells to virulent cells, and he called the component of the dead S-type bacteria the “transforming principle” Fig 11 Schematic diagram of Griffith’s experiment which demonstrates bacterial transformation
What was unique in Griffith’s experiment?
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
Why did heat kill Griffith’s S bacteria?
4 Why did heat kill Griffith’s S bacteria? He found that the bacteria in which the DNA had been destroyed did not transform the harmless strain Griffith used heat to kill the virulent strain but found that the disease-causing ability was still transferred to the harmless strain of bacteria
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 scientist
What did Avery discover about DNA?
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
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
Why did Hershey and Chase use bacteriophages?
Alfred Hershey and Martha Chase used the bacteriophages because of their connection to DNA The phages were mixed with bacteria and because of the way they function, the phages infected the bacterial cells
What are the 3 key roles of DNA?
What are the three key roles of DNA? Storing, copying, and transmitting information
Why did Hershey and Chase use a blender?
After introducing to the phage culture to the bacterial sample, they used a Waring blender to violently disturb the infected bacteria, causing the protein shells to detach from their host
Why protein is not a genetic material?
For a material to be genetic material, it has to replicate, it must be stable both structurally and chemically stable Furthermore, it must be able to provide a scope for mutations eventually, key for evolution
Why did Hershey and Chase use sulfur and phosphorus?
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
What would Hershey and Chase have concluded if they had found radioactive sulfur instead of phosphorus in infected bacteria cells?
If Hershey and Chase had found radioactive sulfur instead of phosphorus in infected bacteria cells they would have concluded that the protein coat of the bacteriophage was involved in the transformation of the E coli 2 The sample of DNA will contain 32 % thymine, 18 % guanine, and 18 % cytosine
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 sulfu
What is the hypothesis for the phage infection experiment?
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
How does a bacteriophage attack a bacteria cell?
To infect bacteria, most bacteriophages employ a ‘tail’ that stabs and pierces the bacterium’s membrane to allow the virus’s genetic material to pass through When the virus attaches to the bacterial surface, the sheath contracts and drives the tube through i
Can bacteria be infected by viruses?
Bacteria can be infected by tiny viruses called bacteriophages (phages) Bacteriophages are so small they do not even have a single cell, but are instead just a piece of DNA surrounded by a protein coa
Do viruses live on bacteria?
Bacteria are also single-celled organisms that reproduce asexually, independently of other organisms Viruses, on the other hand, need the aid of a living cell in order to reproduceCommon illnesses caused by bacteria and viruses:
| Bacterial infections | Viral infections |
|---|---|
| Septicaemia (blood poisoning) | Flu |
Which type of viral infection literally takes over and quickly destroys the host cell?
bacteriophage
What do the viruses do once they leave the host cell?
During release, the newly-created viruses are released from the host cell, either by causing the cell to break apart, waiting for the cell to die, or by budding off through the cell membrane
How does virus multiply?
For viruses to multiply, they usually need support of the cells they infect Only in their host´s nucleus can they find the machines, proteins, and building blocks with which they can copy their genetic material before infecting other cell
What do viruses have in common with living cells?
Still, viruses have some important features in common with cell-based life For instance, they have nucleic acid genomes based on the same genetic code that’s used in your cells (and the cells of all living creatures) Also, like cell-based life, viruses have genetic variation and can evolve
Why do viruses do not show characteristics of life until they enter a living body?
Why do viruses do not show characteristics of life? Viruses lack any membranes Hence, they do not show characteristics of life until they enter a living cell and use its cell machinery to multiply Membrane bound cell organelles are absent
Can viruses infect any cell?
Viruses are by far the most abundant biological entities on Earth and they outnumber all the others put together They infect all types of cellular life including animals, plants, bacteria and fungi Different types of viruses can infect only a limited range of hosts and many are species-specific
Which 3 Characteristics of life do viruses have?
Living characteristics of viruses include the ability to reproduce – but only in living host cells – and the ability to mutat