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Griffiths AJF, Miller JH, Suzuki DT, et al. An Introduction to Genetic Analysis. 7th edition. New York: W. H. Freeman; 2000.

  • By agreement with the publisher, this book is accessible by the search feature, but cannot be browsed.
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An Introduction to Genetic Analysis. 7th edition.

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Introduction

The gene, the basic functional unit of heredity, is the focal point of the discipline of modern genetics. In all lines of genetic research, the gene is the common unifying thread of a great diversity of experimentation. In this chapter, we analyze the patterns in which phenotypes are inherited in plants and animals. We shall see that these patterns are regular and predictable. It was these regular patterns of inheritance that first led to the concept of the gene, and that is where we will begin the story.

The concept of the gene (but not the word) was first proposed in 1865 by Gregor Mendel. Until then, little progress had been made in understanding the mechanisms of heredity. The prevailing notion was that the spermatozoon and egg contained a sampling of essences from the various parts of the parental body; at conception, these essences somehow blended to influence the development of the new offspring. This idea of blending inheritance evolved to account for the fact that offspring typically show characteristics that are similar to those of both parents. However, some obvious problems are associated with this idea, one of which is that offspring are not always an intermediate blend of their parents’ characteristics. Attempts to expand and improve this theory, originally conceived by Aristotle, led to no better understanding of heredity.

As a result of his research with pea plants, Mendel proposed instead a theory of particulate inheritance. According to Mendel’s theory, characters are determined by discrete units that are inherited intact down through the generations. This model explained many observations that could not be explained by the idea of blending inheritance. It also served well as a framework for the later, more detailed understanding of the mechanism of heredity.

The importance of Mendel’s ideas was not recognized until about 1900 (after his death). His written work was then rediscovered by three scientists, after each had independently obtained the same kind of results. Mendel’s work constitutes the prototype for genetic analysis. He laid down an experimental and logical approach to heredity that is still used today. Therefore, although the following description is historical, the experimental sequence is the one still used by geneticists.

By agreement with the publisher, this book is accessible by the search feature, but cannot be browsed.

Copyright © 2000, W. H. Freeman and Company.
Bookshelf ID: NBK21844

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