The reason of the similitude with our parents is genetics. This science studies the inheritance; it means how offspring resemble their parents, the diseases that are transmitted from generation to generation… It is biology’s discipline growing quickly and it affects biology, healthy and society in general. In this article I am going to talk about what is genetics and the DNA’s discovery.
HOW GENETIC INFORMATION IS INHERITED?
The genetic information is inherited to the offspring by genes, which are the storage unit of this information. They are located inside the chromosomes and they occupy specific positions. The number of chromosomes is constant inside species, but different between other species.
In humans the number of chromosomes is 46. In each cell we have 46 chromosomes, which 44 are autosomal, i.e., not a chromosome sexual and 2 chromosomes sexual. The total of 46 chromosomes is the human genome.
Our genome consist of 2 sets of 23 chromosomes counterparts. This means that each set have the same characteristics respect the other set and one comes from our mother by ovum and the other one comes from our father by sperm (Figure 1). Inherit each set of our progenitor is the reason why we resemble they, but also is via that we inherit some genetic diseases.
CHEMISTRY OF GENES
Genes are parts of DNA (deoxyribonucleic acid), comprising by the join of small molecules that called nucleotide. These nucleotides contain a pentose (compound of 5 carbon), a phosphate and a nucleobase (organic compound with an atom of nitrogen) (Figure 2). There are 4 nucleobase: two purines (adenine and guanine) and two pyrimidines (thymine and cytosine). These nucleobases distinguish each nucleotide and their arrangement constitutes the genetic code.
But all knowledge about DNA and genes is recent. The structure of DNA was discovered by James Watson and Francis Crick in 1953 in Cambridge (Figure 3). Previously, other scientists had done studies to try to determine the similarity between relatives, but it was not until this discovery it was understood that there was chemistry behind it.
THE BEGINNING OF THEIR STORY
Watson, an American 23 year-old biologist, and Crick, an English 35 year-old physicist, worked in the Cavendish Laboratory in Cambridge. They spent many months building models of molecules and comparing them to the information they had, but still they couldn’t find the correct structure of DNA.
In the King’s College of London, the physicist Maurice Wilkins and Rosalind Franklin, another physicist with knowledge in crystallography. She took X-ray pictures of DNA (Figure 4).
Watson and Crick, after present a wrong model of the triple helix, told Maurice Wilkins about what they were trying to do and he showed them a new and better X-ray picture of DNA, which had been taken by Rosalind Franklin, without her permission. This was the picture number 51 to help them solve the mystery (Figure 5).
When the university’s Cavendish Laboratory was still at its old site at nearby Free School Lane, the pub was a popular lunch destination for staff working there. Thus, it became the place where Francis Crick interrupted patrons’ lunchtime on 28th February 1953 to announce that he and James Watson had “discovered the secret of life” after they had come up with their proposal for the structure of DNA. This day is called for someone the 8th day of Creation.
The 25th April 1953 it published their article with 900 words in Nature (Figure 6). Three years earlier had published law Chargaff, which was one of the foundations to apply the theory of the double helix of DNA. This law establishes the complementarity of the bases in DNA, i.e., adenine (A) pairs with thymine (T) and the same with guanine (G) and cytosine (C) (Figure 2). So the amount of purine (A and G) is equal to the amount of the pyrimidine (T and C).
THE IMPORTANCE OF GENETICS
It has been argued that the discovery of DNA as well as our understanding of its structure and function may well be the most important discovery of the last century. The effect of the discovery of DNA on scientific and medical progress has been enormous, whether it involves the identification of the genes that trigger major diseases or the creation and manufacture of drugs to treat these devastating diseases. In fact, the identification of these genes and their subsequent analysis in terms of therapeutic treatment has ultimately influenced science and will continue to do so in the future.
While the discovery of DNA has been a significant one in the twentieth century, it will continue to revolutionize medicine, agriculture, forensics, paternity and many other important fields in society today. DNA research encompasses an evolving area of progress and continued funding and interest in its relevance will likely fuel new discoveries in the future.
- Course notes of Genetics, Bachelor’s Degree (UAB)
- Universitat Autònoma de Barcelona: Genetic’s Degree
- Proyecto Biosfera: La materia viva
- The Guardian: DNA double helix
- Explore DNA