Pre 1920:
Fun Fact! Before all of this research and 1950 people thought that genes were like beads on a string.
- 1869: Doctor Friedrich Miescher isolated the first extract of DNA.
- 1944: Oswald Avery did an experiment where he transfered characteristics from one strand of DNA to another showing that DNA carries hereditary information.
Early 1950s:
- Erwin Chargaff found that there were constant quantities of nucleotides in DNA. They were constant in the same species but not in different species. Examples: Adenine=Thymine & Guanine=Cytosine
- Rosalind Franklin realized that DNA was a helix through x-ray diffraction.
- Francis Crick realized there must be a way or system (Messenger RNA/ Central Dogma) to get DNA to transfer to RNA. RNA is a copy of DNA.
- Paul Zamecnik and Mahlon Hoagland found that if they added RNA to an e. coli that was cell-free it stimulated amino acid incorporation into a protein. This means essentially that they found that the template RNA was stimulating protein synthesis cell-free.
- 1957: Matthew Meselson and Frank Stahl proved DNA replicated semi-conservatively which means that two strands separate, but stay single stranded and become grouped with another new strand at each generation.
- 1957-...: Arthur Kornberg was big on enzymes (DNA polymerase) and what they helped in the experiment like catalyzing and directing the assembly of the double helix.
- 1958: Rosalind Franklin dies of ovarian cancer when she is 37
- Maurice Wilkins sees crystal spots on an x-ray of DNA, realizing that DNA is crystalline.
- Linus Pauling believed that DNA was a triple helix. His son and James Watson realized he was wrong.
- James Watson and Francis Crick realized that when he bases were paired it created a double helix. This caused scientists to know three letters that provided combinations to code for all the twenty amino acids called triplet code.
DNA - Cracking the Code
1960s:
By: Seun Kintunde & Stephen Nickisch
- Sydney Brenner conducted more experiments about the messenger RNA.
- Matthew Meselson and Frank Stahl's papers were published in an issue of Nature.
- Francois Jacob and Jacques Monod named the messenger RNA. They created a model of mRNA that could be fumed at different speeds and result in a different speed of the protein.
- Marshall Nirenberg thought that the three bases in DNA corresponded to a single amino acid so there were 64 possible combinations of the three bases. In nucleic acid, the first codon corresponds to an amino acid in a protein. He created a genetic code.Also, he could separate the complex from the RNA by absorption which helps make assay for other codons.
1960s:
- There's a system called the Lac Operon which is a system of feedback and negative regulation that can control the production of proteins.
1962:
- Watson and Crick and Wilkins win the Nobel Prize.
- Easy codons allowed scientists to identify exact triplets that could be used to figure out the rest. They realized that a tRNA molecule that matched a mRNA codon would come together and a nucleotide would be added. The tRNA would then read the sequence and when they separate an amino acid could be identified.
1960s:
- Walter Gilbert knew that molecules should interact with the sugar that came into the cell.
- Benno Muller-Hill modified the bacteria, which had created a mutation that would change the way the repressor would attach to the small molecule.
- Scientists realized that DNA is coiled around proteins and packaged as a chromatin. The uncoiling of DNA controls the production of proteins.