Frederick Griffith Experiment
Frederick was the first British bacteriologist to show the genetic information can be transferred from one cell to the other horizontally rather than by descent. The experiment was a demonstration of bacterial transformation in a process where an external DNA was taken up by a cell changing its morphology and physiology. He worked with Streptococcus pneumonia that causes pneumonia (Abdalla, 2016). Griffith worked with two strains, R (rough) and S (smooth). R is nonpathogenic, and S is pathogenic. The R is named rough as it lacks a capsule appearing uneven under the microscope while S has a capsule and appears smooth under a microscope.
Griffith injected the live R strain into mice, and they survived. In another experiment, he injected another mouse with heat-killed S strain, and the mice died. After isolating the live bacteria from the dead mouse, only the S strain was recovered (Abdalla, 2016). When it was injected into a live mouse, it died. He concluded that something that had passed from the heat-killed S strain into the live R strain transformed it into a pathogenic S strain and called it a transforming principle.
There followed experiments performed by Avery, McCarty, and Chase, establishing that DNA was aa mechanism for the transfer of genetic information between the bacteria. This also led to the discovery of Crick and Watson that discovered the exact structure of DNA and mechanism used for storage and transfer of information Yata, (2016). The research was inspirational, considering that Griffith did not know the chemical and biological processes behind the transformation principle. Griffith had hypothesized that a substance capable of withstanding heat treatment could be transferred from killed S strain to R strain.
References
Abdalla, K. O. (2016). The Structure and Function of DNA-Part I. http://repository.gaduniv.edu.sd:8080/xmlui/bitstream/handle/123456789/274/L8%20DNA%20structure%20%26%20function.pdf?sequence=1&isAllowed=y
Yata, T. (2016). Development of efficient amplification method of DNA hydrogel and composite-type DNA hydrogel for photothermal immunotherapy. https://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/215494/3/dykkk00056.pdf