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Charles Darwin shares his Theory of Evolution
Charles Darwin worked in the development of this theory during 20 years, and this theory has changed everyone's point of view. It wasn't very clear, but the teory involved some things that were a bit similar to the DNA concept. -
First DNA Indefication
Friedrich Miescher discovered DNA existency in late 1860's, eventhough lots of people think James Watson and Francis Crick did it in 1950's. -
Gregor Mendel discovers the Basics of Genetics
Considered as the father of genetics, between 1856 and 1863 Mendel conducted experiments on pea plants. He identified seven characteristics: plant height, pod shape and colour, seed shape and colour, and flower position and colour. Mendel described the action of 'invisible' factors in predictable way, and these 'invisible' traits he had identified were the genes. -
Archibald Garrod Associate Mendel's theories with a Human Disease
These association could be the first concept pretty similar to the genetic diseaeses, but the idea wasn's clear enough to considere it as the "discovery". -
Levene's Tetranucleotide
Levene's theory consisted on every molecule having four nucleotides, and that DNA could'nt store the genetic code because it had such a simple structure. -
Griffith's Transformation Experiment
Done by Frederick Griffith in 1928, this experiment suggested that bacteria was capable of transfering genetic information through transformation. Griffith used two strains of pneumococcus bacteria which infect to mice. A type III-S which was virulent, and a type II-R which was nonvirulent. The III-S strain synthesized a capsule that protected itself from the immune system, which killed the host, while the other did not have that protective capsule, and the host survived. -
Explanation of Transformation (Avery, MacLeod and McCarty)
These 3 scientists determined the cause of the transformation in Griffith's experiment, mixing R and heat-treated S mixed in some enzymes, proteases and DNase's. -
Erwin Chargaff discovers that DNA composition is different in each Specie.
After analysing lots of different DNA from several species, Chargaff said that the proportion of DNA varies between species. Eventough, in every specie, all the A's are the same as amount of T's, and the same happens with C's and G's. This discovery are now known as 'Chargaff's Rules'. He also discovered an inportant factor that helped the discovery of the DNA double hèlix. -
Double Helix structure is Firstly Thought
In 1951, Watson and Crcik wrote a paper in which they describes DNA as a double helix with sugars and phosphates at the centre, with nucleobases at the outside. This model was shown as chemicaly incorrect and was quickly shown that had no sense. -
Hershey - Chase Experiments
he Hershey–Chase experiments were a series of experiments done by Alfred Hershey and Martha Chase in 1952 that helped to confirm that DNA is genetic material. In their experiments, Hershey and Chase showed that when bacteriophages, which are composed of DNA and protein, infect bacteria, their DNA enters the host bacterial cell, but most of their protein does not. -
Triple Helix Model
Linus Pauling thought in a triple helix structure with, again, sugars and phosphates at the centre, with nucleobases at the outside. -
Definitive Double Helix Structure Model
In 1953 James Watson and Francis Crick published their theory that DNA must be shaped like a double helix. A double helix resembles a twisted ladder. Each 'upright' pole of the ladder is formed from a backbone of alternating sugar and phosphate groups. This theory would have been imposible without Rosalind Franklin's photo 51, which was a photo about the DNA structure, and it was very helpful for determining Watson and Crick's theory. -
First DNA Genetic Disease Discovery
Huntington's Disease was the first ever genetic disease discovered, and it was located in Chromosome 4. Allthough, genetic diseases had been present lots of years ago. -
"Dolly the Sheep" is cloned
Dolly the sheep was the first mammal to be cloned from an adult cell, and was created by scientists from the Roslin Institute in Scotland, from the udder cell of a Finn Dorset white sheep. -
First Human DNA Decoding
When Human Chromosome 22 was first decoded in 1999, it became the longest stretch of DNA ever assembled.