On the inheritance of certain invisible characters in peas

Abstract

In a paper which appeared recently in the ‘Proceedings of the Royal Society,’ Messrs. Bateson and Punnett and Miss Saunders showed that the visible appearance of certain characters in Sweet Peas and in Stocks was due to the association together in the same zygote of factors belonging to independent but complementary allelomorphic pairs. If both the complementary factors were not simultaneously present, no hint of the presence of the characters in question was to be detected without breeding tests; nevertheless, the presence and absence respectively of such a factor constitute a pair of allelomorphs, and segregate in complete accordance with Mendel’s law. The present communication deals with a similar but somewhat simpler phenomenon exhibited by certain colour characters of the testa of the ordinary field or garden pea―the species to different cultivated varieties of which the names Pisum sativum and P. arvense have been given. The case is simplified by the fact that here only one of the two complementary factors is by itself invisible. The presence of the second factor is invariably accompanied by the appearance of a definite visible character, whether the invisible factor is present or not. The present examples of “latency” are of special interest on account of the classical nature of the material, as well as because it has been suggested that Mendel was in error in his own account of the characters of the testa in peas. It may be stated at once that this is not the case. Mendel’s account is perfectly correct so far as it goes. The grey colour of the testa, constantly associated with coloured flowers and coloured axils, is a simple Mendelian dominant to colourless testas coupled with white flowers and green axils.