Genetic, Chemical, And Functional Characteristics

Beginning in the mid 1800’s, Gregor Mendel discovered that hereditary factors determine an organism’s physical, chemical, and functional characteristics but would take many years before being accepted . Once Mendel’s work was rediscovered in the 1900s, scientists began to search for the molecule involved in inheritance that led to the discovery of deoxyribonucleic acid (DNA) the hereditary material present in the cells of all living organisms. In 1928, Frederick Griffith performed the first major experiment that led to the discovery of DNA by studying two strains of the pneumococcus bacteria. Of the two strains he studied, one caused pneumonia (lethal) and had a smooth appearance while the other strain did not cause pneumonia (non-lethal)†¦show more content†¦Then exposing live non-lethal cells to the macromolecules separately. When the live non-lethal cells were exposed to the lethal strain DNA, they were transformed into lethal cells. Avery concluded that when the lethal cells in Griffith’s experiments were killed, DNA was released. Some of the non-lethal bacteria incorporated this DNA into their cells, and this changed the bacteria into lethal cells. Avery’s conclusions were not widely accepted in which many scientists continued to question and experiment to determine whether proteins or DNA were responsible for the transfer of genetic material. In 1952, Alfred Hershey and Martha Chase published results of experiments that provided defining evidence that DNA is the transforming factor. These experiments involved a bacteriophage, a type of virus that infects bacterial cells. Three components made the experiment ideal for confirming that DNA is the genetic material: First, they are easy and inexpensive to maintain; second, they can produce new viruses rapidly by injecting a part of themselves into a host cell; and third, bacterial viruses consist simply of a core of DNA surrounded by a protein coat. Hershey and Chase then labeled both parts of the virus to determine which part was injected into the bacteria and which part was the genetic material. Using a technique called radioactive labeling, Hershey and Chase were able to trace the outcome of the