Conclusion

Date: 2015-10-07; view: 466.

Genetics - the science of heredity and variation - was developed in the early XX century. After researchers drew attention to the laws of Mendel, discovered in 1865, but was ignored for 35 years. In a short time has grown into an extensive genetics biological science with a wide range of experimental methods and direction. Name of genetics was proposed by the British scientist William Bateson in 1906, researchers of the classical period of genetics clarified the basic laws of inheritance and prove that hereditary factors (genes) are located in the chromosomes. Further progress in the study of the laws of storage and realization of genetic information held back for two reasons. First, because of too much space experiments associated with a more profound study of genes, and secondly, due to the inability to understand the workings of genes without an in-depth study of the transition of molecules involved in genetic processes. The transition to genetic studies of microorganisms, avoiding many of the difficulties was quite natural. This transition was realized in the first 50 years. In 1941, George Beadle and E. Tatum has published a short article, "Genetic control of biochemical reactions in Neurospora", which reported the first genetic experiments on micro-organisms. In recent years, these studies were widespread and carried out on a variety of biological systems. The origin of the chromosome theory of heredity. Experiments on Plant Hybridization. Accumulation of information about heritable traits. Attempts to understand the nature of the transmission characteristics inherited from parents to children date back to antiquity. Reflections on the subject are found in the writings of Hippocrates, Aristotle and other thinkers. In XVII-XVIII's., When biologists began to understand the process of fertilization and look with what you start - male or female - is connected secret fertilization, the debate about the nature of heredity resumed with renewed vigor. In 1694, RJ Kammerariusom found that fruit set to be pollinated. Thus, by the end of the XVII century. was prepared by a scientific basis for the beginning of the experiments on the hybridization of plants. The first success in this direction has been made in the beginning of XVIII century. Interspecific hybrid was first Englishman T. Fairchild crossed with a nail. In 1760 began the first Kolreuter carefully designed experiments to study the transmission of traits in crossing plants. In 1761 - 1766 years., Nearly a quarter century before L. Spallanzani, Kolreuter in experiments with tobacco and clove showed that after the transfer of pollen to the pistil of one plant differs in plant morphology formed ovaries and seeds, giving plants with properties intermediate with respect to both parents. The exact method developed Kolreuter, led to rapid progress in the study of inheritance of attributes. In the late XVIII-early XIX century. English breeder - grower TE Knight, spending crossing different varieties, makes an important conclusion. An important finding was the discovery of the Knight of the indivisibility of small signs at various crossings. Readability of the hereditary material, proclaimed in ancient times, was in his first scientific research study. Knight is credited with opening the "elementary inherited traits." Further significant progress in the development of methods of crosses are associated with O. and S. Sazhre Nodenom. A major achievement was the discovery of the phenomenon of Sarzhe dominance. Varieties when crossed, he often watched by suppressed one parent sign the other. This phenomenon manifests itself as much as possible in the first generation after the crossing, and then depressed again signs were detected in children of the next generation. Thus Sarzhe confirmed that elementary hereditary traits in crosses disappear. This conclusion was reached Noden in 1852 - 1869 years. Noden but went a step further by launching the quantitative study of hereditary transition combinations in crosses. But on the way he was disappointed. Invalid methodical technique - simultaneously studying a large number of signs - led to great confusion in the results, and he was forced to abandon his experiments. Disadvantages. inherent Nodena experiences and his predecessors, have been eliminated in the work of Mendel. Practice development hybridization led to the further accumulation of information about the nature of mating. Practices required to address the issue of maintaining the same characteristics of "good plant, and to reveal how the combination of a single plant right features inherent to several parents. Experimentally address this issue was not yet possible. Under such circumstances, there is a variety of speculative hypotheses about the nature of heredity.