Demonstrating the Anatomical Expression of Two Genes in the Garden Pea

Abstract

Traits studied in introductory genetics courses are chosen because of their distinct mutant phenotypes. These traits often affect the external morphology of the organism, such as vestigial wings in the fruit fly, albinism in corn, and potato-shaped leaves in the tomato. Such traits are excellent for illustrating genetic principles, but because they have no economic significance, students may fail to recognize the practical applications and importance of genetics. Many genes have been identified that affect traits such as disease resistance, growth rates, nutritional content, and appearance of the commercially used parts of plants. Examples include the sugary gene in sweetcorn, the high-lysine genes in corn and sorghum, and the dwarf genes in the green revolution rices and wheats. King (1974) provides additional examples. These genes are economically important to farmers and distributors of produce. We describe here a rapid staining technique for studying the anatomical expressions of two such genes in the pea. These genes illustrate the economic importance of major genes, the phenotypic expression of genes at the anatomical level, and pleiotropy (multiple phenotypic expressions of a single gene). In addition, they are historically interesting, because one of the genes was used by Mendel in his classical inheritance studies with peas (Novitski and Blixt 1978).