This is a timeline depicting different significant discoveries made abour DNA
Created by AminRashidi on Apr 14, 2011
Last updated: 04/14/11 at 12:17 PM
Watson and Crick studied the X-ray diffraction data collected Rosalind Franklin, and proposed that a spiral staircase to the DNA structure. They also managed to hypothesize the concept of base pairing between nucleotides. Each strand of DNA or RNA have two nucleotides that pair with each other on opposite side. Thusly, A is more stable with T, while G is more stable with C. Then these two complementary sides are linked by hydrogen bonds.
The two scientist ran a series of experiments to confirm that DNA carried the genetic material, and not protein (which scientists had thought). These experiments were called the Martha-Hershey experiment. Although the Avery-MacLeod-McCarty had already demostrated that DNA was the genetic material, the Hershey-Chase experiment with T2 phage virus, had confirmed it.
Although her discovery might be controversial, she is accredited with discovering a double helix structure in the DNA by using a technique called X-ray diffraction.
The three scientists, Colin MacLeod, Oswald Avery and Maclyn McCarty, hypothesized that Fred Griffith's controlled experiment with bacteria had a flaw. Fred Griffith did not treat the cells at a high enough temperature to denature their DNA, and thusly the three scientists completed the experiment, and were the first to demonstrate that the Transforming Principle was DNA. In other words, DNA transmits hereditary.
Erwin Chargaff is mainly renowned with the discovery of two main principles; Chargaff's rules. His first, and most important, rule explains that in a natural DNA, the number of adenine is equal to thymine, and the number of cytosine is equal to guanine. For example, in Human DNA the percentages are: A=30.9% and T=29.4%; G=19.9% and C=19.8%. This rule disproved Phoebus Levene's hypothesis that ATGC are present in equal amount in DNA.
Through experiments that lasted around 15 years, Griffith was able to identify a principle called the "Transformation Principle". Fred Griffith tested mainly with bacteria, and was able to conclude that bacterium can distinctively change its form and function. Unfortunately, Griffith died during World War II and thus could not discover what caused this transformation.
Upon Miescher discovery of nucleic acids, Phoebus Levene further continued studying these structures. He managed to differentiate between the two types of nucleis acids, RNA and DNA. Thus making him the sole discoverer of these organelles. Levene also found that DNA contained adenine, guanine, thymine, cytosine, deoxyribose, and a phosphate group.
Friedrich Miescher was able to isolate a phosphate-rich substance from white blood cells. The young Swiss biologist and physician, called this material "nuclein". He then later determined that nuclein was made up of two substances: acidic portion (nucleic acid) and alkaline portion (protein)
Gregor Mendel is credited with the findings on the transmission of hereditary information, through a method that was called "Mendel's Punnet Square". He showed that inheritance of traits followed particular laws, which was later on named after him.