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Modern Genetic Analysis Chapter 1. Genetics and the Organism
Summary

Genetics is the study of genes at all levels, from molecules to populations. As a modern discipline, it began in the 1860s with the work of Gregor Mendel, who first formulated the idea that genes exist. We now know that a gene is a functional region of the long DNA molecule that constitutes the fundamental structure of a chromosome.

Genetics has had a profound impact on human affairs. Much of our food and clothing comes from genetically improved organisms, and molecular genetic engineering is expanding the scope of applied genetics. In addition, a large portion of human illness has a genetic component. Genetic research has also provided important insights on the way we see ourselves in relation to the organic world and to the rest of the universe.

Genetics has revolutionized biology by showing that most organisms on the planet work on a common information storage and expression system, centered on DNAa system in which information flows from DNA to RNA to protein. Genetic dissection, moreover, is an incisive analytical tool used in all the biological sciences.

Genes do not act in a vacuum, but interact with the environment at many levels in producing a phenotype. The relationship of genotype to phenotype across an environmental range is called the norm of reaction. Most of the major advances in genetics have come from laboratory studies on characters having a simple, one-to-one correspondence of genotype to phenotype. However, in natural populations, phenotypic variation generally shows a more complex relationship to genotype and not a one-to-one correspondence. Discontinuous variants have been the starting point for most experiments in genetic analysis. Often distinct phenotypes of a character are determined by alleles of a single gene.

The main tools of genetics are breeding analysis of variants, biochemistry, microscopy, and DNA cloning.

© 1999 by W. H. Freeman and Company. All rights reserved.