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. |
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 |
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. |
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 |
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 |
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. |