Question

The key part of Griffith's experiment was showing that....

Select one:

a. Bacteria could become transformed with new abilities because of infection by a virus (phage) which brought in DNA from another organism

b. Bacteria could acquire antibiotic resistance genes from dead bacteria

c. Bacteria could pick up genes for producing toxins from dead bacteria

d. Bacteria that couldn't form a capsule could get the ability to form one from dead bacteria

e. Bacteria could acquire antibiotic resistance genes from their environment

Answer 1

Option d

Bacteria that couldn't form a capsule could get the ability to form one from dead bacteria.

Frederik Griffith performed an experiment in the year 1928 to find the genetic material. He performed the experiment using R and S strains of the bacteria Streptococcus pneumoniae. R strain colonies have  a rough appearance due to the absence of the capsule and it is a non-virulent strain whereas the S strain bacterial colonies are smooth due to the presence of a thick capsule and this strain is virulent. S strain is virulent because it get protected from the host's immune system due to the presence of the capsule.

Mice injected with S strain die due to infection whereas mice injected with R strains show no effect. Griffith injected mice with heat killed S strain and the mice survived. Finally Griffith injected mice with a mixture of heat killed S strain with a R strain and the mice died, he was surprised with the result.
Griffith concluded that a chemical substance from the S strain might have taken by the R strain that has transformed the R strain into to a virulent form. After transformation R strains could able to grow the capsule, which has made them virulent.