Chapter 7, Problem 1P

What results from the experiments of Frederick Griffith provided the strongest support for his conclusion that a transformation factor is responsible for heredity?

Summary Introduction

To analyze:

Study the results of the Frederick Griffith experiment to analyze the conclusion that the transformation factor is responsible for heredity.

Introduction:

In $\text{1928}$, British bacteriologist Frederick Griffith performed a series of experiments to determine the genetic material in organisms. Today all know that the DNA is the hereditary material in all living organisms, excepting some viruses. The discovery of DNA as hereditary material took place after the discovery of transforming principle.

Explanation of Solution

In $\text{1928}$, British bacteriologist Frederick Griffith performed a series of experiments to determine the genetic material in organisms. Frederick Griffith used two related strains of Streptococcus pneumonia, which causes pneumonia, for his experiments. One was R strain or resistant strain, and second was S strain or sensitive strain. The R strain causes pneumonia while S strain does not cause pneumonia. Frederick Griffith performed a series of experiments with mice to study the effect of both strains on mice.

In the first experiment, Griffith tried injecting mice with s strain and the mice died. Secondly, the mice were injected with heat-killed S strain of streptococcus, but surprisingly no death of mice was found. In the third experiment, the mice were injected with R strain, but no death occurred. Finally, when the heat-killed R strain of streptococcus was combined with harmless heat-killed S strain of streptococcus, he found that the mice are dead and the blood samples of the mice contain living S bacteria.

The transformation of R strain to s strain in mice supports the conclusion that Frederick, the transformation factor, causes the heredity.

Conclusion

From Frederick Griffith’s experiment, it is concluded that the transformation factor is responsible for heredity.