Answer :
Final answer:
Frederick Griffith conducted experiments in the 1920s using mice and two strains of Streptococcus pneumoniae to demonstrate bacterial transformation. His work highlighted the lethal effects of the virulent S strain compared to the non-virulent R strain. This foundational research contributed significantly to the understanding of genetic material and transformation processes.
Explanation:
Griffith's Experiments with Mice
In the 1920s, American scientist Frederick Griffith conducted pivotal experiments involving mice and the bacterium Streptococcus pneumoniae. He examined two different strains of this bacterium: the virulent S (smooth) strain and the non-virulent R (rough) strain. In his experiments, Griffith injected these strains into mice to observe their effects.
The S strain was lethal, killing the infected mice, while the R strain did not harm them. Interestingly, when he heated the S strain to kill the bacteria, the mice remained healthy. However, when Griffith mixed heat-killed S strain with live R strain bacteria and injected this combination, the mice died. This result indicated that some transforming material from the dead S strain bacteria was taken up by the living R strain, rendering them virulent.
Griffith's findings were groundbreaking as they demonstrated a process known as bacterial transformation, laying the groundwork for future research into genetics and the role of DNA.
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