Chapter 13, Problem 1TYU

In his work with pneumonia-causing bacteria and mice, Griffith found that

1. a. the protein coat from pathogenic cells was able to transform nonpathogenic cells.
2. b. heat-killed pathogenic cells caused pneumonia.
3. c. some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.
4. d. the polysaccharide coat of bacteria caused pneumonia.

Summary Introduction

Introduction:

Griffith has conducted experiments on mice by injecting live and dead strains of bacteria inside their bodies. The experiments revealed that some material was present in the strain of bacteria, which caused the infection in mice. He injected live and attenuated strains of bacteria in mice. The mice, which were injected with heat attenuated strains survived, but the mice, which were injected with live strains of the bacteria died.

After this step, he injected both live and attenuated strains of bacteria and observed that some substance caused the death of these mice by converting the attenuated strain into a live strain of the bacteria into these cells. This process of the transfer of genetic information is called as “transformation”. The substance was found out to be smooth and rough coat of polysaccharides present on the outer surface of the bacteria.

Answer to Problem 1TYU

Correct answer:

The infection of the mice with a live strain of the bacteria caused infection as compared to the injection of the heat attenuated strain of the bacteria, which prevented infection. Therefore, option (C) is correct.

Explanation of Solution

Reason for the correct statement:

The infection of the mice with heat attenuated strains prevented the death of bacteria, but infection with the live strains of bacteria caused the death of bacteria in the Griffith experiments. The infecting substance was found out to be the rough and smooth coat of the polysaccharide present on the surface of bacteria. The smooth coat was found to be pathogenic and rough coat non-pathogenic.

Option (C) is given as “some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic”.

“In his work with pneumonia-causing bacteria and mice, Griffith found that some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic”, it is the right answer.

Hence, option (C) is correct.

Reasons for the incorrect statements:

Option (A) is given as “the protein coat from pathogenic cells was able to transform nonpathogenic cells”.

The protein coat of polysaccharides consists of smooth and rough strains, but the death of mice was due to the live strain as compared to the heat attenuated strain of bacteria. So, it is a wrong answer.

Option (B) is given as “heat-killed pathogenic caused pneumonia”.

The heat killed bacteria are non-pathogenic and did not cause disease. So, it is a wrong answer.

Option (D) is given as “the polysaccharide coat of bacteria caused pneumonia”.

The disease, pneumonia was caused due to the polysaccharides present on the surface of bacteria that were not attenuated by heat killing method. So, it is a wrong answer.

Hence, options (A), (B), and (D) are incorrect.

Conclusion

The experiments of Griffith concluded that the death of mice was caused by injecting of live strains of bacteria as compared to the heat killed dead strains of bacteria