Principles of genetics applied to medicine.

Genes and environment interact continuously throughout life, from the moment of conception, to regulate and affect all aspects of human structure and function. The normal rules of mendelian inheritance, ie, the transmission of genes over the generations, are usually best studied by observation of abnormal mutations, especially in plants and animals under precise breeding conditions. The study of such didactic models as the guinea pig crosses discussed here is a prerequisite to an understanding of mendelian genetics in man and the terms used in other articles to appear in this series.