Talk:Frederick Griffith
From Wikipedia, the free encyclopedia
 |
This article is within the scope of WikiProject Biography. For more information, visit the project page. | ||
| Stub | This article has been rated as stub-Class on the Project's quality scale. [FAQ] (If you rated the article, please give a short summary at comments to explain the ratings and/or to identify the strengths and weaknesses.) |
||
During the early 1900s, the study of genetics began in earnest: the link between Mendel's work and that of cell biologists resulted in the chromosomal theory of inheritance; Garrod proposed the link between genes and "inborn errors of metabolism"; and the question was formed: what is a gene? The answer came from the study of a deadly infectious disease: pneumonia. During the 1920s Frederick Griffith studied the difference between a disease-causing strain of the pneumonia causing bacteria (Streptococcus peumoniae) and a strain that did not cause pneumonia. The pneumonia-causing strain (the S strain) was surrounded by a capsule. The other strain (the R strain) did not have a capsule and also did not cause pneumonia. Frederick Griffith (1928) was able to induce a nonpathogenic strain of the bacterium Streptococcus pneumoniae to become pathogenic. Griffith referred to a transforming factor that caused the non-pathogenic bacteria to become pathogenic. Griffith injected the different strains of bacteria into mice. The S strain killed the mice; the R strain did not. He further noted that if heat killed S strain was injected into a mouse, it did not cause pneumonia. When he combined heat-killed S with Live R and injected the mixture into a mouse (remember neither alone will kill the mouse) that the mouse developed pneumonia and died. Bacteria recovered from the mouse had a capsule and killed other mice when injected into them!
Hypotheses: 1. The dead S strain had been reanimated/resurrected. 2. The Live R had been transformed into Live S by some "transforming factor". Further experiments led Griffith to conclude that number 2 was correct. In 1944, Oswald Avery, Colin MacLeod, and Maclyn McCarty revisited Griffith's experiment and concluded the transforming factor was DNA. Their evidence was strong but not totally conclusive. The then-current favorite for the hereditary material was protein; DNA was not considered by many scientists to be a strong candidate.
He concluded that something in the dead virulent cells “transformed” the hereditary material of normally harmless bacteria so that they became killers. it is the virus’s DNA—not protein—that enters the bacterium to cause infection. Their studies confirmed that DNA contained the virus’s genetic information, which triggered viral replication within the bacteria This meant that genes existed as physical things which were preserved even after the organism died, and that this genetic material can be transferred from one organism to another while preserving its function.
