Matthew Meselson and Franklin Stahl Are Two Biologists Who Prove That Dna Replication Was Semiconservative
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Matthew Meselson and Franklin Stahl are two biologists who prove that DNA replication was semiconservative.
At the time, many strong evidences from experiments using bacterial viruses had already convinced most scientists that DNA was the molecule of heredity; however they knew little about the DNA replication process. After the dimensionally accurate model building by Watson and Crick, it was clear that the process of replication and information distribution have to use the DNA from parent cell as template to achieve an orderly flow of genetic inheritance to daughter cells. However the model of Watson and Crick still cannot fill the missing information about how DNA might accomplish replication.
Before the Meselson-Stahl experiment, many researches have been done on the problem of DNA replication by other scientists, but all of those efforts were ineffective or not directly relate to the replicate process. There were three hypotheses suggested; which are Semi-Conservative, Conservative and Dispersive. The first possibility is Conservative replication; one daughter cell receives the original DNA that was used as template, while the other daughter cell receives only newly replicated strand of DNA. The second possibility is Semiconservative replication; each daughter cell receives only one strand of DNA from the parent cell, while the complementary strand is newly replicated. The third possibility is Dispersive replication; each daughter cell receives a new double-strand that consists of distinct regions of DNA from either original or new strands interspersed throughout out the strand (Templin & Fetters 2002).
In 1956, Meselson and Stahl began to carry out an idea that Meselson had earlier had to investigate the problem by incorporating a heavy isotope into the DNA molecules of a microorganism and tracing the distribution of these atoms into progeny DNA by separating molecules of different density in a centrifuge. The plan of their landmark experiment on DNA replication was to grow the organisms in the heavy medium, transfer them to the light medium, withdraw samples at the time intervals representing successive cell generations, lyse the bacteria to release their DNA, and centrifuge the