Good Old Days Or The History Of Genetics

History of Genetics

People must have noticed family likenesses and traits long long ago but they were generally mysterious things appearing and disappearing with the generations touching. Some off spring skipping others inheritance was inextricably linked with reproduction, and some understanding of how it worked had to wait for the Greeks and Aristotle. In particular he studied the development of chicken eggs and concluded that the embryo and his organs developed from the tissue in the egg a process called epigenesis.In higher animals the mother and father somehow both made contributions. In mammals the menstrual blood and semen each somehow drawing characteristics from the whole bodies of the parents. They combined it was an idea that was to be revived in the Renaissance and persist until the 19thcentury as pangenesis, Charles Darwin faded. Little real progress beyond an appreciation the great achievements was made until the changing attitudes of the Scientific Revolution and the invention of the microscope.

The discovery of the microscope

Just before 1600 in an age of enthusiastic deception this revealed not just fascinating external details but also complex internal structures and the development incest through the larval pupil and adult stages it showed the sperm wriggling through the seminal fluid. Some Bookmen parasites but they were soon seen as the agents of reproduction. Spallanzani begun experiments in which he fitted male frogs with well-tailored gingham trousers and found that they prevented fertilization is often quoted perhaps misleading. and to the explanation of inheritance preformation how try for a long time this claimed that each offspring for all future generations existed right from Adam and Eve perfectly formed but absolutely minute. In either the egg or the sperm it may be difficult now to see how this could be credible but in various sponsor has accepted. But then the creation is the idea of the chain of being was widely accepted to certainly up to the middle of the 18th century. This organised creation into a series of layers with God at the top and angels than humans then apes and then layers of other animals, plants were somewhere below that and then there were rocks and other inanimate things at the bottom.

The chain had plenitude and continuity plenitude because the Creator being perfect have already created everything that shouldbe and continuity because everything had to be neatly connected. So species were fixed in the scheme and hybrids and by the end of the 18th century men were known were seen as a real challenge.

The golden age of genetics

 The discovery of the sexuality of plants in the 18th century was a great shock to believers and provoked outrage. Plants with their multiple sex organs seem to be having too good a time. Science nibbled away at the chain fossils were a particular problem but the creationist interpretation was hardly challenged publicly until the 1840s Charles Darwin.At the middle of the century confronted it in his Origin of Species. The careful work about so easy in monk Gregor Mendel in the 1850s and 60s probably directed at resolving questions over the fixity of species mark the beginning of the science of genetics.Mendel studied the inheritance of several well-defined traits in peas and further the pattern of this could be explained if there were two factors determining the trait one inherited from the mother and one from the father.

Mendel's experiment 

One of Mendel's traits was pea color where it seemed that these two factors could come in two forms first : green and yellow. If a plant inherited green factors from both its parents then all the peas would be green. If both were yellow this peas will be yellow. The peas are a plant having one green factor and one yellow one might have been thought to be greenish yellow but in fact they were always yellow. Yellow was the dominant factor and green the recessive. The other striking result was that inheritance of the factors was a random process. A parent with a green and a yellow factor would pass on one or the other to his offspring with equal probabilities.

 Mendel's results could have been an important insight in the search for the physical basis of inherentance.But alas! although published in 1865 it was hardly known until we discovered at the turn of the century. The study of the cell became more fruitful from the 1830’s as microscopes better images and preparation techniques improved. It was recognized that all plants were composed of cells and the discovery of mitosis followed soon after the internals of the cell house on the nucleus were being studied by the 1870s. There was good reason to think by the 1880s that the key to inheritance away in the nucleus.

Beginning of modern genetics

By about 1900 there was strong evidence from the work of Theodore Bovary that the newly discovered chromosomes were carriers. Mendel's work strongly supported this. When rediscovered the behaviour of the chromosomes was consistent with that of his factors important in the 1880s was August Weismann as promotion of the germplasm theory. This had it that heredity worked solely through the germ cells and that these were unaffected by the other cells of the body which here was what was called a Wiseman barrier. It was warm to Sutton working at Columbia University in 1902 who produced clinching evidence from his work on the grasshoppers clinching for many. Anyway and truly coherent theory of the role of chromosomes in heredity has become known as the Sutton Bovary theory while this provided at theory of Mendelian inheritance.There were several issues that did not address for example it did not explain quite how non discrete traits such as height were inherited although it was soon to be adapted. To do so it did not explain why some factors were dominant and others recessive.

And so we arrived at the new century and the years around this mark three key events the emergence of USA as the real driving force and much of genetics research. The start of the career of a tiny fruit fly Drosophila melanogaster the black-bellied do lava has superb experimental subject and just a little earlier the birth of our human subject Herman Joseph Muller in New York in 1890.

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