Combinations of Characters 243 



over albinism, and short hair is dominant as against long hair. 

 The mating of a black short-haired animal with a long-haired 

 albino will yield in the first hybrid generation short-haired 

 black animals resembling in both traits one of the parents 

 — that is, the dominant (see Fig. 63 ) . 



The descendants of a hybrid pair that show recessive 

 characters continue to produce " pure " offspring, notwith- 

 standing their hybrid parentage and their mixed ancestry. 



TY 



DG 



TY 



-J- 



9 Tall yellow -f 3 Tall green -h 3 Dwarf yellow -h 1 Dwarf green 

 Fig. 62. Heredity of Two Pairs of Contrasting Characters 



On mating a tall plant bearing yellow seeds (TY) with a dwarf plant bearing 

 green seeds {DG) , the hybrids resulting (F,) all resemble one parent, TY , since 

 tallness and yellow-seededness are both dominant over their alternatives. Although 

 these hybrid plants resemble their dominant parents in both characters, they do 

 not breed true: on mating they yield in the next generation (F2) four distinct 

 kinds of individuals, showing the four possible combinations of size and seed 

 color. The proportions in which these four combinations appear are also signifi- 

 cant. Out of every sixteen plants there are 9 tall yellow-seeded, like their hybrid 

 parents (that is, dominant in both characters); i dwarf green seeded, like the 

 lost grandparents (that is, recessive for both characters); and three each of tall 

 green-seeded and dwarf yellow-seeded (that is, dominant for one trait and re- 

 cessive for the other.) The classical 3:1 ratio is perhaps concealed among these 

 large numbers, but note that among all the green-seeded plants as well as among 

 ail the yellow-seeded ones there are three tails to one short. Similarly, among 

 all the tall plants as well as among all the dwarfs there are three yellows to 

 one green. 



