Coupling The term introduced by Bateson, Saunders and Punnett (1905) for the condition (phase) of a heterozygote for two linked character differences in which the two dominant factors were derived from one parent and the two recessive factors from the other. This condition may be represented as A B - a b, where A/a and B/b represent the two character-differences and the capital letters indicate the dominants. The slash separates the contribution from each parent (Cf. Repulsion).