DNA: History and Structure

DNA, the molecule carrying the genetic instructions of life, was arguably one of the most important discoveries of the last century.

DNA: History and Structure


DNA: History and Structure


1859 - Charles Darwin’s The Origin of Species

Before the publication of this book, people had a different view of life. The book was highly controversial because it rejected many religious beliefs at that time. His idea of evolution that apes are human forefather proved untrue by modern scientists. But animals change themselves in the changing environment, reproduce and thus continue their existence is proven. 


1866 Gregor Mendel’s Law of Genetics An Augustan priest, George Mendel was pretty ahead of his time to experiment on pea plants and crossbreed them to find out the laws of genetics. However, it took thirty years for the others to take his work seriously and thus declared George Mendel as the Father of Genetics as a recognition of his work.


1869 Friedrich Miescher identifies DNA as ‘Nuclein’ Like George Mendel, he was also ahead of his own time as he identified DNA in white blood cells and named it ‘Nuclein’. His discovery was 50 years ahead and the later scientist understood its importance.



The 1900s - The Eugenics Movement

Eugenics movement refers to the "science" of heredity and good breeding was a new chapter in DNA history. Mendel's theories on height and color were rediscovered in 1900. The darker side of the movement was 'scientific' racism which means researchers involved themselves in breeding human beings with the best genes. It was not good for humanity.


1900 – Mendel’s theories rediscovered

16 years after his death, scientists like Hugo de Vries, Carl Erich Correns and Erich Tschermak von Seysenegg rediscovered George Mendel’s theory independently.


1902 – Mendel’s theories with a human disease

Sir Archibald Edward Garrod is the first who associates the theories with any human disease. The disease was alkaptonuria, a recessive disorder in humans. It also showed for the first time that error in chemical flow causes a genetic disorder. 


1944 – DNA, the ‘transforming principle’

Oswald Avery proves that it is DNA, not genes are the ‘transforming principle’, the discrete units of heredity. At first, he worked on bacteria-related diseases but then he wanted to find the substance responsible for the transformation. With Colin MacLeod and Maclyn McCarty, he purified twenty gallons of bacteria and became sure that the substance was nothing but DNA. 


1950 – Composition of DNA is species-specific

Erwin Chargaff took the work of Oswald Avery very seriously and began to work on the chemistry of nucleic acids. He was successful in analyzing the nitrogenous components and sugars of DNA from different species. He continued his research resulting in analyzing DNA for a wide range of species. His two findings are a) the composition of DNA varies between species; b) the number of adenine units is equal to thymine units and the guanine units are equal to cytosine units in a double-stranded DNA. 


1952 - Crystallized DNA fibers photographs

Being a lady and become a scientist of DNA was nearly impossible in those days. But Rosalind Franklin did it very well in 1952. She along with Maurice Wilkins and Raymond Gosling used the X-ray crystallography unit to take two sets of photographs with high resolution. The photographs were helpful to get an actual idea about the dimension of the DNA.


1953 -The double helix DNA structure 

James Watson and Francis Crick used X-Ray data and model building and their effort was successful. They were awarded the Nobel Prize along with Maurice Wilkins for their double helix DNA model. Rosalind Franklin’s photograph was of equal importance but she was deprived of the award as three scientists were already on the list. 


1953 - George Gamow forms The “RNA Tie Club” 

After the invention of DNA’s double helix model, scientists started to discover genetic code. George Gamow formed an exclusive club named “RNA Tie Club”, consisting of 20 members analyzing one amino acid each. But the fun fact is that Marshall Nirenberg discovered the genetic code and he was not a member of the club.   


1959 - Chromosome 21 linked to Down's syndrome

Although it took many years to recognize the study of chromosomes diagnosing disease. For this, they linked an additional copy of chromosome 21 Down's syndrome. The introduction of Giemsa made it possible to identify individual chromosomes.


1965 - Marshall Nirenberg cracking 'life's code'

Based on his research on nucleic acids and protein synthesis, Marshall Nirenberg and Matthaei experimented on E-coli bacteria. His research showed a repeating chain of uracil that forces another protein chain consisting of amino acid, phenylalanine. All his efforts paved him the way to sequence the code of life for the first time was jointly awarded the Nobel Prize in 1968 with some other scientists.


1977 - Development of rapid DNA sequencing techniques  

While deciphering the genetic code and spelling out the sequence of amino acids in proteins were going on in the 1970s, Frederick Sanger came with the development in finding precise nucleotide sequences of DNA. He first applied his rapid sequencing techniques in the RNA and then moved to DNA. His sequencing technique was a milestone in this field and he got Nobel Prize for chemistry in 1980.


1983 - First genetic disease mapped

Huntington's disease (HD) is the first-ever disease mapped on by using DNA polymorphisms. The disease comes into being at the age of 30 to 45 but the genes of the disease are passed on the next generation before its diagnosis. It took 10 years to finally isolate the gene in 1993.

Barbara McClintock worked on maize chromosomes with microscope analysis and gave her idea about genetic recombination by crossing-over during meiosis. Her discovery established her as a Nobel Laureate in Medicine in 1983. In 1990 Familial breast and ovarian cancer’s first gene is identified

Scientists researched large families having characteristics related to hereditary breast-ovarian cancer (HBOC) syndrome and performed DNA linkage studies on them. They named the gene BRCA1 located on chromosome 17 and further found BRCA2 located on chromosome 13. These two genes can lead to tumor formation in the future.


1990 - The Human Genome Project starts

After recommending a program to map the human genome, The National Research Council started the Human Genome Project officially in 1990. The mapping of the human genome is the key to advanced medicine. It is also helpful in the study of biology and the technical development of DNA analyzing. 


1995 - First bacterium genome sequenced

Haemophilus Influenzae is the harmful bacteria that cause meningitis and respiratory infections in children. So, scientists needed to research on that. They applied "shotgun" sequencing, a new strategy to sequence the genomes completely for the first time. Their strategy was more effective and less time-consuming in finding the complete genome sequence for some viruses. 


1996 - Dolly, the cloned sheep

Cloning from embryo cell was a common practice, but cloning from adult cells became successful after scientists of the Roslin Institute in Scotland cloned Dolly, the sheep from an adult cell. Scientists reprogramed the cell by altering the growth medium. They removed the nucleus from an unfertilized egg and injected the cell into it. After all this, they implanted the egg into a surrogate mother. Among the 277 attempts, Dolly was the one to see the light.


1996 - 'Bermuda Principles' established

The leaders of the Human Genome Project attended the summit held in Bermuda in 1996. They all agreed that the information regarding genome sequence is vital for the advancement of healthcare and research. The 'Bermuda Principles', is the result of the summit which ensures genome data’s availability in the public domain within 24 hours of generation.


1999 – Human chromosome decoding

The major achievement in DNA research was found at the ending time of the 20th century. The researchers were able to unravel the full genetic code of a human chromosome for the first time in 1999. They considered chromosome 22 containing 33.5 million chemical components. In terms of deciphering and assembling, the sequence was the longest. It was a torchbearer to others to lead the research further.



2000 – Fruit fly’s genetic code decoded

Following the effective results of human chromosome decoding, the scientists first decoded the genetic code of fruit fly as its biology and development are nearly common with the mammals. This achievement was a step forward to achieve the ultimate goal.


 2002 – Mouse’s genetic code decoded

The mouse is the first mammal whose genome was decoded after the human genome. Now the scientists have two mammals to compare to find out similarity and dissimilarity. They found that most of the mammals were genetically related as they found 90% of the mouse genome can be aligned with the human genome. There were 3000 common protein-coding genes between the two. 


2003 – Finishing the Human Genome Project 

The dream comes true in 2003 as the Human Genome Project was finally completed. Started 15 years earlier, this journey is proved to the longest and the most fruitful one. By 2001, scientists were able to find out a 90% sequence and in 2003 they completed 99% accurately. This project results in resolving 2.85 billion nucleotides among the 3 billion nucleotides and thus the scientists achieved the goal to find out Charles Darwin’s suspect that human characteristics are inherited.                            


2013 - Twins are different

There are some certain differences in genetic makeup between the twins and researchers proved it in 2013. Before this discovery, it was believed that twins are 100% genetically identical. But the scientists implemented many processes like combining bioinformatics with next-generation sequencing, sperm samples DNA sequencing of the twins and blood sample of a twin’s child. They found five differences.


2014 - Further achievements

By the year 2014, scientists have developed an organism containing expanded artificial genetic code. This organism will eventually lead to producing medicines or industrial products organically.  We are already getting its benefits as the scientists have found out that 100 genes are responsible for schizophrenia. Now they can find a cure for it soon.  In 2015 March, DNA from an extinct woolly mammoth is spliced into that of an elephant. Scientists then successfully use the "revived" DNA to sequence the mammoth's complete genome.