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Laws of inheritance - Gregor Mendel
Gregor Mendel deduced the laws of inheritance. -
Discovery of nucleic acids - Friedrich Miescher
Friedrich Miescher isolated for the first time in history the genetic material from white blood cell nuclei.
He noticed it had an acidic nature and called it nuclein. -
Discovery of DNA Components - Phoebus Levene
Defined phosphate-sugar-base units called nucleotides
He characterized the different forms of nucleic acid, DNA from RNA, and found that DNA contained adenine, guanine, thymine, cytosine, deoxyribose, and a phosphate group. -
The transformation Experiment - Frederick Griffith
Frederick Griffith was researching a vaccine to prevent pneumonia.
He used two strains of the Streptococcus pneumoniae bacterium. The S strain contained a polysaccharide capsule and was virulent when injected, causing pneumonia and killing guinea pigs within a day or two. This capsule allowed the bacteria to resist the attacks of the immune system. The R strain was not virulent, and did not cause pneumonia, because it lacked a capsule.
Type S: virulent (deadly)
Type R: non-virulent (harmless) -
The discovery of DNA - Phoebus Levene
Levene stated that nucleic acid was deoxyribonucleic acid composed of four nitrogenous bases (cytosine (C), thymine (T), adenine (A) and guanine (G)), a deoxyribose sugar and a phosphate group, and that its basic structure was a sugar linked to a base and a phosphate. he proved. -
DNA is the carrier of biological information - Avery, MacLeod and McCarty
They determined the cause of the transformation in Griffith's Experiment.
They took live R and heat-treated S and mixed it with one of two enzymes:
a protease (destroys protein)
a DNAse (destroys DNA)
Studies on the Chemical Nature of the Substance Inducing Transformation of Pneumococcal Types: Induction of Transformation by a Deoxyribonucleic Acid Fraction Isolated from Pneumococcus Type III
DNA not protein was responsible for the bacterial transformation Griffith observed. -
Description of DNA - Watson and Crick
Watson and Crick wrote a paper in which they described DNA as a double helix with sugars and phosphates at the center and the nucleobases facing the outside.
This model was quickly shown to be incorrect and in fact it made no chemical sense. -
Counting Nucleobasesm - Erwin Chargoff
He used paper chromatography and UV spectroscopy to examine the abundance of the nucleobases and he started to notice something very odd:
Came to be known as "Chargoff's Rules"
Amounts of Adenine = Amounts of Thymine
Amounts of Cytosine = Amounts of Guanine
It's always in every species -
Hershey-Chase Experiments - Hershey and Chase
He used phages and radiolabeled phosphorus and sulfur
Hershey and Chase concluded that DNA, not protein, was the genetic material.
A protective protein coat was formed around the bacteriophage, but the internal DNA is what conferred its ability to produce progeny inside bacteria. -
Meselson and Stahl's experiment - Meselson and Stahl
In this experiment they demonstrated that DNA replication was semi-conservative using the N14/N15 isotopes. Bacteria cultured with N15 were taken and incubated in N14 medium. Then, by means of ultraviolet rays, they saw that the newly synthesized DNA was in between, the DNA containing N15 and half of it containing N14. In view of the new hybrid DNA they concluded that the conservative hypothesis of replication was incorrect and proposed a semi-conservative one. -
Discovering the bases of adenine and thymine - Albercht Kossel
Albercht Kossel discovered the bases adenine and thymine. When studying nucleoproteins, he realized that part of them was protein and the other part was not protein (nucleic acids).