Evolution of Genetics: From Philosophy to Science - Essay Example

Evolution of Genetics: From a philosophy to science Inserts His/Her Inserts Grade Inserts (14th June 2010) Evolution of Genetics: From a philosophy to science Genetics has its roots dating back to the ancient notions proposed by Aristotle and Hippocrates, which was later represented as a concept by Darwin. Later on by observation and studies by Weismann, Mendel and Crick this philosophy evolved into a science. Charles Darwin was a zoologist and naturalist, whose greatest contribution to science came by his theory of natural selection. These were the one of its kind in helping the later scientists understand that how biological development took place. Darwin’s theory of evolution, contributed to genetics by introducing the concept of natural selection. This theory proposed that all the life on planet Earth, human or non-human is interrelated and has roots to a common ancestor. This means that the life indeed has evolved from non-life i.e. the simple creatures led to the evolvement of complex creatures over time. This all was possible because random genetic mutations were taking place in the genetic code of the living organism. So every complex organism, for instance, the human being, was formed after several successful modifications and mutations took place in the earlier generations. By the natural selection process, the dominant traits would be preserved and carried forwarded to the future generations. As the dominant traits were the beneficial ones they would be transferred ahead, where as the recessive traits would be the non-beneficial ones and they would fail to transfer to the next generation. With this transference of beneficial mutations, the preservation of the functional advantages is there in the offspring. The idea was that such a mechanism existed where any changes in the external stimuli would lead to a change in the external organ and external tissues. This would be further transferred on to the reproductive organs consequently affecting the offspring. Further, the process of natural selection, as proposed by Darwin is a gradual and time-consuming process, which never takes any quantum leaps. (Darwin, Glick & Kohn 1996) So today, our biological development can be understood by understanding Darwin’s theory. In Darwin’s time, the genetic mutations were just a philosophy. His ideas led to further research which helped the scientists understand that biological development does involve structural changes in the chromosomes. Then August Weismann was a German biologist whose work led him to be one of the pioneers in the study of genetics. Weismann‘s major work revolved around embryonic and postembryonic development of insects. His work was greatly inspired by Darwin’s theory of evolution and that is why his work is also known to the world as Neo-Darwinism. Weismann’s initial contribution came in from his embryological study of Hydra. By this he proposed that in living organisms there are some predetermined cells that lead to evolution of the individual daughters. This was the germ plasm concept, which explained that certain substance was transmitted from generation to generation in the living organism. This substance he termed as germ plasm was a predetermined substance that came from a preexisting cell and could not be formed on its own. This germ plasm theory further introduced the heredity aspect to it. It suggested that each cell’s heredity substance should be called the Idioplasm. Each living organism’s cell has an Idioplasm which constitutes of smaller components called Ids. The id is in fact having groups of the simplest living substance called Biophors. These together are responsible for the heredity and development of each living organism; as Germ Plasm is carried forward by the chromosome from generation to generation by the reproductive cells. So Weismann contributed to the genetics by proposing that in heredity, each parent would be transferring some distinct units for each heredity trait. (Dodson & Dodson 1976) Furthermore, besides the Germ Plasm theory, Weismann made other contributions to evolution of genetics. Weismann through his research contributed that in the process of meiotic division of gametes, the occurrence of crossing took place. This he substantiated further was the key process which was responsible for gene mutation; the idea which was the very essence of Darwin’s theory of evolution. Next, George Mendel’s works on the common garden pea led to a new revolution in genetics. Mendel started by introducing a basic concept of paired heredity factors, which now we call as genes. Mendel proposed that each trait of living beings is actually an output of a set of genes, which we call alleles. The alleles can both be same and different. In case the alleles are different, then each of the two in the set of the gene is going to affect the trait being exhibited in a different way. This is so as both of the alleles can act in a different way. Or it can be that only one of the alleles is having an effect and it is indeed cancelling out the effect of the other allele. Mendel here led genetics to understand that the allele which is cancelling out the presence of the other allele’s characteristics is the dominant gene. Where as the allele which is unable to show its presence due to the effect of the dominant allele is to be known as the recessive gene. Mendel’s theories came up with identifications for the set of genes. When two genes are different in a pair then an individual would be known as heterozygous in nature. When the two genes are same in a pair then they are to be known as homozygous in nature. This observation also helped the scientists understand that the recessive genes can only exhibit their presence if it is homozygous. So the recessive genes as per Mendel’s proposition are visible in only few cases where an offspring is inheriting two copies of the recessive genes from the parents. In such scenario, the dominant genes are completely absent and consequently the characteristics of the recessive genes are visible. Hence, Mendelian genetics initiated when George Mendel observed seven characteristics in pea plants were inherited independent of each other and every one of the characteristics had two traits each. (Walter 2010) So Mendel presented two basic laws for genetics; first, during the process of meiosis, the genes separate each going to one gamete and each gene in uninfluenced by the other, this was the law of segregation. Second was his law of independent assortment which explained that the characteristics inherited are independent of each other. But Mendel’s key contribution was the observation that two genes are controlling the phenotypes; and these genes can be dominant and recessive in nature. This research basis later contributed to the fact that in humans, the independent inheritance of characteristics is likely only when the genes which are responsible for there presence are found in 23 sets of different chromosomes in our DNA which make up our genome. Thus, Mendel’s research formed the basis of modern genetics. From the Darwin’s philosophy to formation of modern genetics by Mendel, each individual came up with a breakthrough theory that helped science evolve into more concrete but complex facts. One such breakthrough in modern molecular biology and genetics was made by Francis Crick. The milestone achieved by Francis Crick and his fellow James Watson was the discovery of the three dimensional twisted ladder like, double-helix structure of the DNA i.e. the Deoxyribonucleic acid. (Watson & Crick 1953) This led to the ground breaking discoveries into understanding that how the genetic code, the chemical process within the cells and the protein synthesis actually worked. This development has led to advancements in biotechnology, genetic engineering and modern forensics. The research done by Crick was able to show that how the DNA is having pairing of bases inside its backbone where A=T and C=G. Crick explained by the pairing rule that in DNA a copying mechanism existed by which the sequence of bases in one strand would automatically determine the sequence of the other strand. Further, if the two strands would ever separate then each strand would be serving as an automatic pattern for a new pairing strand. Crick by his research was also able to advocate that DNA could replicate its own copies as each molecule on the strand was carrying some genetic instructions. Crick followed this research by further developments. He proposed a general hypothesis about the organization of RNA i.e. Ribonucleic acid and proteins in viruses. And lastly, but not the least, he contributed to genetics by identifying the mechanisms involved in the process of protein synthesis. When he explained about the ‘Central Dogma’ by which he implied that changes in a protein cannot be inherited. This was a conformation to the earlier work by Darwin in his theory of evolution. Further, Crick substantiated through rigorous research that all the genetic codes found in DNA are universal in each form of life. Hence, with time, each one of the researcher made some new contribution on basis of the work done by those before them and this led to the evolution of genetics as a science and not just a philosophy. References Charles Darwin, Thomas F. Glick, David Kohn. On evolution: the development of theory of natural selection. Hackett Publishing, 1996. Edward Ottway Dodson, Peter Dodson. Evolution: process and product. Van Nostrand, 1976. Herbert Eugene Walter.Genetics, and An Introduction to the Study of Heredity. Read Books, 2010. J. D. Watson, F. H. C. Crick. "A structure for Deoxyribose Nucleic Acid." Nature 171 (1953): 737–738. Read More