AP BIOLOGY

Detailed explanation-1: -Studies on DNA and gene transfer were initially described in Streptococcus pneumoniae (Griffith, 1928). In 1928, Frederick Griffith proved that an avirulent pneumococcus strain was able to acquire lethal properties from a pathogenic variant from what was thought to be based on protein transfer (Griffith, 1928).

Detailed explanation-2: -In 1928, British bacteriologist Frederick Griffith conducted a series of experiments using Streptococcus pneumoniae bacteria and mice. Griffith wasn’t trying to identify the genetic material, but rather, trying to develop a vaccine against pneumonia.

Detailed explanation-3: -Frederick Griffith performed experiments on Streptococcus pneumoniae which is responsible for causing pneumonia. He observed that the bacteria produce two colonies as: R strain: rough colonies which are non-virulent. S strain: smooth colonies which are virulent and caused the death of mice.

Detailed explanation-4: -Griffith concluded that the type II-R had been “transformed” into the lethal III-S strain by a “transforming principle” that was somehow part of the dead III-S strain bacteria. Today, we know that the “transforming principle” Griffith observed was the DNA of the III-s strain bacteria.

Detailed explanation-5: -Frederick Griffith’s experiments with strains of Streptococcus pneumoniae provided the first hint that DNA may be the transforming principle. Avery, MacLeod, and McCarty proved that DNA is required for the transformation of bacteria.