In 1865 an Austrian monk, Gregor Mendel, presented the results of painstaking experiments on the inheritance of the garden pea. Those results were heard, but not understood, by Mendel's audience. In 1866, Mendel published his results in an obscure German journal. The result of this was that Mendel's work was ignored and forgotten. Mendel died in 1884 without knowing the pivotal role his work would play in founding the modern discipline of genetics.
By 1899, some geneticists were beginning to realize the necessity of mathematically analyzing inheritance in order to understand how evolution might work (Bateson, 1899). They did not realize that Mendel had already solved this problem. Then, in 1900, three leading scientists of the day, Hugo de Vries, Carl Correns, and Erik von Tschermak, simultaneously rediscovered Mendel's paper and realized how important it was. With the rediscovery of Mendel’s principles, genetics as a scientific discipline exploded into activity. Within two years, the first human study of inheritance (Garrod, 1902), describing the Mendelian inheritance of alkaptonuria, was published. This paper, too, was far ahead of its time, the importance of which would only be recognized as the one gene-one polypeptide principle was developed in the latter part of this century.
Now, more than a century later, Mendel's work seems elementary to modern-day geneticists, but its importance cannot be overstated. The principles generated by Mendel's pioneering experimentation are the foundation for genetic counseling so important today to families with health disorders having a genetic basis. It's also the framework for the modern research that is making in roads in treating diseases previously believed to be incurable. In this era of genetic engineering - the incorporation of foreign DNA into chromosomes of unrelated species - it is easy to lose sight of the basics of the process that makes it all possible.
Recent advances in molecular genetics have resulted in the production of insulin and human growth hormone by genetic engineering techniques. Cancer patients are being treated with cells that have been removed from their own bodies, genetically altered to enhance their tumor destroying capacity, and then reinserted in the hope that microscopic tumors escaping the surgeon's scalpel may be destroyed.
This newfound technology has not been without controversy, however. Release into the environment of genetically engineered microorganisms that may make crops resistant to disease-causing organisms (or even capable of withstanding temperatures that normally would freeze plants) has met with strong opposition.
In the future, you may be called upon to help make decisions about issues like these. To make an educated judgement, you must understand the basics, just as Mendel did. This exercise will give you a better understanding of the basic laws that govern the inheritance of characteristics by successive generations.
The corncob is not the fruit of the corn plant in itself, nor are the kernels the seeds. Each kernel of corn is really a fruit, which develops from the ovary of one of the female flowers of the plant. There are a great number of inheritable characteristics in corn (Zea mays). In this experiment we will investigate two, the color of the kernel and starchy consistency of the endosperm which gives rise to wrinkled or smooth kernels.
The endosperm is a nutritional reserve for the developing corn seedling that provides energy to the seedling after immediately germination. This reserve is drawn on until the developing plant begins to generate its own energy by photosynthesis. Three layers of cells protect the endosperm. The inner most layer, the aleurone layer, contains purple pigments called anthocyanins. The amount of anthocyanin in the aleurone layer and the amount of starch present in the endosperm are genetically determined and can be inherited according to Mendelian...
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