Griffith called the process he observed transformation because

a. the mouse had been transformed.
b. the harmful bacteria had been transformed.
c. the harmless bacteria had been transformed.
d. the experiment had been transformed. previous next

The correct answer would be the harmless bacteria had been transformed.

Griffith used two different strains of the bacteria Streptococcus pneumoniae - type-III-S or smooth strain and type II-R or rough strain.

Smooth strain had protective covering around itself (protect itself from hosts's immune system) and was able to kill the mice.

Rough strain did not have any protective covering around itself  and thus could be easily removed by the immune system Hence, it was not able to kill the mice.

In addition, heat killed smooth strain was also not able to kill the mice. However, when remains of it was added with rough strain then the blend was able to kill the mice.

Lastly, he was able to isolate living bacteria of both the strains.

He concluded that non-lethal type II-R strain was transformed into lethal type II-S strain by "transforming principle" (which we know today as DNA) that was supposed to be the part of dead III-S strain bacteria.

Griffith experimented and concluded that harmless bacteria could be transformed from one strain to another strain.

Further Explanation:

Frederick Griffith is a scientist who experimented with the mouse in 1928. He concluded that bacteria could acquire DNA by the process mainly referred to as transformation. In his experiment, he used two kinds of strain of Streptococcus pneumoniae. In this experiment, he infects mice with this bacterium.

Type-II R strain of bacterium is a rough strain and does not encapsulate with a layer of the polysaccharide. Another strain is Type-III S, which smooth strain and covered with the polysaccharide. This polysaccharide layer protects bacteria from immune cells present in the host. In this experiment, type-II S strain is injected in the mouse by the heat-killed method by which this strain has died. Type-II R is injecting normally and kills the mouse. Through this Griffith concluded that Type-II R strain is converted into lethal Type-III S strain by transforming principle.

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Answer Details:

Grade: High School

Subject: Biology

Topic: Transformation

Keywords:  Transformation, mice, strain, streptococcus pneumonia, experiment, lethal, mouse, smooth strain, rough strain, transforming principle, normal, kill.

Griffith called the process transformation because the harmless bacteria had been transformed. So the answer is 'C'.

Explanation:

Griffith performed an experiment on the mouse in which he worked on two different strains of streptococcus. One of the strain  was capable of causing disease (virulent) III-S and the other was a rough strain which was non virulent type II-R. He injected different combinations of the strains. The heat killed smooth strain became non virulent.

The most important discovery he made was that when heat killed smooth strain and rough strain were introduced together in the mice and the mice died. It happened because the rough strain of bacteria transformed into virulent form as the DNA from heat killed smooth strain was imbibed by the rough strain which converted into virulent form.

c. The harmless bacteria had been transformed.  

Explanation:

Fredrick Griffith carried out the first experiment that showed bacteria can get DNA by transformation in 1928.

He used two different strains of the bacteria Streptococcus pneumoniae a)type-III-S or smooth strain-Covered by a protective polysaccharide capsule hence lethal

b) type II-R or rough strain-Lacked the polysaccharide hence non-lethal

In his experiment he observed heat killed Type-III-S strain was not able to kill the mice. However, when its remains was added with rough strain then the blend was able to kill the mice.

When he collected blood  from the dead mice it had live strains of both smooth and rough type.

He came to a conclusion that non-lethal type II-R strain was transformed into lethal type II-S strain by a "transforming principle"  that was supposed to be the part of dead III-S strain bacteria.