Understanding Heredity: An Introduction to Genetics

Understanding Heredity: An Introduction to Genetics

Understanding Heredity: An Introduction to Genetics

Understanding Heredity: An Introduction to Genetics

Excerpt

It is no exaggeration to say that there is no one who has not, at some time, concerned himself with questions of heredity. After all, when you look at a child to see which parent it resembles, when you look for a man's supposed racial characteristics, when you recognize in a friend or relative features you had once noticed in his uncle or grandfather, when you observe that some of the puppies in a litter are piebald and some are solid colored, or when you buy seed of a particular variety of flower or vegetable, in every such instance you assume, consciously or unconsciously, that hereditary characters are involved, passed somehow from ancestor to offspring. You sense, however obscurely, that some rule, some orderly process, must lie behind these inheritances. You may even try to find the rule or process. It will not take you long to discover that the situation seems hopelessly confused. Your own children may faithfully exhibit your own or your spouse's brown eyes, curly hair, Roman nose, slender limbs, very short little finger, emotional responsiveness, etc.; your neighbor's numerous family, on the other hand, may seem to have inherited no feature, physical or mental, from their parents, and the several brothers and sisters may seem to have little or nothing in common. In short, no generally applicable interpretation may seem possible. Yet judgment should be reserved, for more thorough investigation may establish order out of the confusing facts. Closer study may show which traits are transmitted to future generations and which are buried with their possessor, and may reveal how it is that now one, now another type of inheritance appears in what seem to be only bewildering mixtures.

Just such difficulties led to many detours in the quest for laws of biological inheritance before the science of heredity, genetics, could firmly establish the fundamental facts and prin-

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