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It’s been ages since people have tried to discover that mysterious secret of life – the chain of generations, the making of the individual, so different, but so similar, which creates the entity…
In this project I would like to introduce you to the history of Genetics, that is how in the space of years the phenomenon of heredity and changeability has been observed and how men have carried out investigations on the laws ruling differences and similarities of the individual, connected with the human origin and its role in today's world.
Genetics is a comparatively young science, because it came into being practically at the beginnings of last century and just from these beginnings it has played an important part among the fields of Biology. For hundreds of years it was believed that "similar gives birth to similar”. The most important task of a living organism is to give birth to posterity to make the species survive. This process had always been a matter of study and researches among the scientists, who, in the course of the Centuries, formulated different theories. The most important was Darwin’s
Charles Darwin, who was born in England in 1809, became one of the most popular natural scientist in the History of Science. Darwin devised by far the best documented Theory of Evolution. During his five year travels around the world he collected a great quantity and quality materials about animals and plants from every corner of the globe. He observed a phenomenon which he named “Fight for Life” – every plant and animal has to fight for food and survival; only the organism which is best adapted to the environmental conditions has a chance to survive.
Darwin came to the conclusion that this is the explanation of the wide variety of species living on the Earth. In the whole world there is a lot of environments that differ one from the other. Furthermore, Darwin maintained that adaptation required a long time. When he returned to England he collected even more documents which supported his opinion; in 1859 he announced his Theory in his well known work "The Origin of Species". At the beginning Darwin’s ideas were quite unpopular and laughed at.
Nowadays they are the basis for modern Genetics and Microbiology.
The beginnings of Genetics date since 1865, when the Czech Gregor Mendel released his experiment works on green peas. Presently, he’s known as the person who discovered the basis of Genetics and was named “the father of genetics”. In his life he was an unknown monk but a passionate scholar. His studies were not considered by scientists of his own time; in fact, his researches were revalued in 1900 separately by three other scholars – Hugo de Vries, Charles Correns and Erich von Tschermak – who shared Mendel’s Theories on Heredity. From his experiments (carried out in a garden next to the convent) on the heredity of peas Gregor Mendel concluded that basic elements, nowadays named genes, exist in every living organism in the world. In the plants, which Mendel researched, individual features like the colour of seeds or the shape of leaves were determined by an individual pair of genes. Every specimen receives one gene from each chromosome of its parents. Mendel found that if the genes from one pair were different (e.g. one gene characterizing high growth, and the other low growth), only the stronger one, called the dominant would show. However, the weaker gene, called recessive, wouldn’t disappear but could be passed on to the next generation. Mendel understood that every reproductive cell (both the egg and the spermatozoa) receives only one gene from every pair. He also found that the gene from the pair will be passed on by accident. According to the principle of Independent Assortment, different pairs of alleles are passed to offspring independently of each others. Today we know that the genes for independently assorted traits are located on different chromosomes. The result is a wide variety of features in the future generations.
In spite of that during the following years Genes were still esoteric elements of heredity and people couldn’t situate them in a cell. Only researches into the Drosophila melanogaster – fruit fly – carried out by Thomas Hunt Morgan allowed to place genes in cellular structures, called Chromosomes. These experiments were awarded the Nobel prize in 1933. Morgan demonstrated that genes, are arranged in chromosomes like stripes, and they are passed on from cell to cell in a process of cellular division and the similar mechanism of passing on the genes takes place during the division, called Meiosis, leading to the formation of sperms and eggs. In this process the number of Chromosomes is reduced to half. Fecundation permits the union of the two pools of Chromosomes – and of their genes – which recreates the correct number of chromosomes, previous to meiosis.
Having known the effect of meiosis and fertilization, it was understood why Mendel’s First Law says that an even number of genes determines a given feature. It became clear that his Second Law concerns the genes accumulated in different Chromosomes. Nowadays, we can mention Thomas Morgan’s theory of heredity. Thanks to Morgan, present Science has also got the possibility of mapping genes in the grounds of Chromosomes. He proved that there is the possibility to find (under a microscope) the stripes – places of genes in suitable uncoloured huge Chromosomes of the fruit fly. Thanks to this discovery the first maps of genes in chromosomes of different organisms could be made.
Morgan’s conclusions were additionally supported by Francis Crick and James Watson and their researches on the structure of DNA. In 1961 Crick advanced the hypothesis that the particle of DNA appears like a double helix of nucleotides. The sequence of three neighbouring nucleotides is known as coding triplet or codon and codifies a specific aminoacid.
Nirenberg worked out the method to read the genetic code. The statement that genetic code is universal, that is, the same codon codifies the same aminoacid both in bacterium and in man was by the far most important.
Until lately, narrowly specialized scientific fields, like genetics had been the object of interest only for small team of experts explorers. Now, reports from the news of Genetics are diligently followed by a lot of people. The progress of Genetics not only helps in many diseases (vaccine against hepatitis virus of B type), but is also a challenge for us, for which Mankind is not prepared yet. Therefore it’s necessary to be careful in every direct or indirect interference in DNA and we should remember that on the background of every investigation, the increasing development of sciences, the various opinions, there is one word which may sound so strange, so different, but is always the same: