In his work with pneumonia-causing bacteria and mice, Griffith found that a. the protein coat from pathogenic cells was able to transform nonpathogenic cells. b. heat-killed pathogenic cells caused pneumonia. c. some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic. d. the polysaccharide coat of bacteria caused pneumonia.

Verified step by step guidance

1. Step 1: Understand the question. This question is asking about Griffith's experiments with pneumonia-causing bacteria and mice, and what he discovered through these experiments.
2. Step 2: Recall the details of Griffith's experiments. Griffith worked with two strains of Streptococcus pneumoniae bacteria: a pathogenic strain that caused pneumonia, and a nonpathogenic strain that did not. He found that when he killed the pathogenic bacteria with heat and mixed them with the nonpathogenic strain, the nonpathogenic bacteria became pathogenic.
3. Step 3: Evaluate the answer choices. Option a is incorrect because Griffith did not find that the protein coat from pathogenic cells was able to transform nonpathogenic cells. Option b is also incorrect because heat-killed pathogenic cells alone did not cause pneumonia. Option d is incorrect because the polysaccharide coat of bacteria did not cause pneumonia.
4. Step 4: Choose the correct answer. The correct answer is option c: some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic. This is a description of Griffith's discovery of what he called 'transforming principle', which was later found to be DNA.
5. Step 5: Review the chosen answer. Griffith's experiments were a major step in the development of molecular genetics, as they provided the first hint that genes could be physically transferred from one organism to another.

Key Concepts

Transformation

Transformation is a process in which a cell takes up foreign DNA from its environment, leading to a change in its genotype and phenotype. In Griffith's experiments, nonpathogenic bacteria were transformed into pathogenic forms by acquiring genetic material from heat-killed pathogenic bacteria, demonstrating that DNA carries genetic information.

Griffith's Experiment

Frederick Griffith conducted experiments in the 1920s using Streptococcus pneumoniae to investigate bacterial virulence. He discovered that when nonvirulent bacteria were mixed with heat-killed virulent bacteria, the nonvirulent bacteria became virulent, indicating that some 'transforming principle' was responsible for this change, later identified as DNA.

Pathogenicity

Pathogenicity refers to the ability of an organism, such as bacteria, to cause disease. In Griffith's study, the presence of a polysaccharide capsule in pathogenic strains of bacteria was crucial for their virulence, as it helped evade the host's immune response, leading to pneumonia in infected mice.