Q. No.Heat-killed S form Streptococcus extract treated with proteases is mixed with live R form Streptococcus cells and injected into living mice. What is most likely to happen?
| 1. | The mice would live. |
| 2. | The mice would die. |
| 3. | The mice's blood would have dead R cells. |
| 4. | A new strain of Streptococcus will be present in mice. |
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Which of the following possible modes of replication was eliminated by Meselson and Stahl based on the finding after one generation of replication of the bacterium?
| 1. | Dispersive | 2. | Semi-conservative |
| 3. | Conservative | 4. | Both 1 and 3 |
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Griffith wanted to make a vaccine to prevent pneumonia. He injected heat-killed S-strain bacteria into the mice for this purpose. How can a killed bacteria help in making a vaccine?
| 1. | The heat-killed bacteria is a more potent toxin than the live one. |
| 2. | Protein denaturation due to heat changes the proteins of the bacterium. |
| 3. | Molecules from the cell surface are still intact and can provoke an immune response. |
| 4. | DNA molecules can transform other strains of bacteria. |
Avery, MacLeod, and McCarty used DNase in their experiment because:
| 1. | It enabled them to isolate pure DNA samples. |
| 2. | It enabled them to isolate pure protein samples. |
| 3. | This allowed them to demonstrate that removing the DNA prevents transformation. |
| 4. | It made sure that RNA will always be present when they attempted to transform the R strain. |
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Griffith's experiment discovered bacterial transformation which in his experiment means:
| 1. | A mutation in the R strain made them virulent. |
| 2. | A mutation in the S strain made them non-virulent. |
| 3. | A rough strain passed genetic information to a smooth strain. |
| 4. | A smooth strain passed genetic information to a rough strain. |
T2 bacteriophage was used by Hershey and Chase to conclusively prove that DNA and not protein is the genetic material because:
| 1. | It makes capsomeres with the help of its genes. |
| 2. | It injects its genetic material into a bacterial cell. |
| 3. | It can undergo either the lytic or lysogenic life cycle |
| 4. | It enters the bacterial cell to cause infection. |
What radioactive isotope was used in Meselson and Stahl experiment to prove the semi-conservative mode of DNA replication?
| 1. | 35S | 2. | 32P |
| 3. | 15N | 4. | None |
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Griffith co-injected the heat-killed S and live R strains of Pneumococcus bacterium into the mice and much to his surprise the mice developed pneumonia and died. He concluded that:
| I: | Live R was transformed into Live S strain as he was able to isolate Live S strain from the blood of the infected mice. |
| II: | Bacterial transformation is a stable and heritable change as the culture of bacteria isolated from dead mice was unable to infect other mice. |
| 1. | Both I and II are correct |
| 2. | Only I is correct |
| 3. | Only II is correct |
| 4. | Both I and II are incorrect |
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What key observation regarding Garrod'sinborn of metabolism leads to a landmark discovery in molecular biology?
| 1. | Identification of a defective gene in individuals with alkaptonuria. |
| 2. | Identification of a defective gene in parents of alkaptonuria patients. |
| 3. | Identification of a defective enzyme in individuals with alkaptonuria. |
| 4. | Identification of the inheritance pattern of alkaptonuria as autosomal recessive. |
I. The lack of 35S-labeled DNA remaining in the solution after the bacteriophages had been allowed to adsorb to the bacteria showed that the phage DNA was transferred into the bacterial cell.
II. The presence of almost all the radioactive 32P in the solution showed that the protein coat that protects the DNA before adsorption stayed outside the cell.
| 1. | Only I | 2. | Only II |
| 3. | Both I and II | 4. | Neither I nor I |
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