GENETICS 241 



16. If two parents which haVe the same visible characters produce some offspring 

 wliich are hke the parents, some different, write the formulas of the parents using any 

 symbols you choose. 



17. In squashes, white fruit is dominant over yellow. From a certain cross 

 between a white- and a yellow-fruited plant, 54 white and 59 yellow offspring were 

 obtained. What were the formulas of the parents, if squashes were primitively yellow 

 like pumpkins? 



18. One flower of a white-fruited squash plant A is pollinated from another white- 

 fruited plant B, and both white and yellow progeny are produced. Another flower 

 of plant A is pollinated from a yellow-fruited plant and produces 44 offspring. How 

 many of these should be white? 



19. A third flower of plant A in problem 18 is self-fertiUzed and produces 44 

 offspring. How many of these should be white? 



20. Two gray female mice are mated with a black male. In several litters the 

 first female produces 12 gray and 10 black offspring, the second female 19 gray. 

 What are the formulas of the two females? Use your knowledge of wild mice in 

 determining part of your answer. 



21. Pink eye in mice is recessive to the wild-type dark eye color. From a certain 

 mating between two dark-eyed mice some dark- and some pink-eyed mice are obtained. 

 The male is then mated with a pink-eyed female, and they produce, in several litters, 

 20 offspring. How many of these should be pink-eyed? 



22. Uniform or self-color in mice is dominant over spotting. A self-colored mouse 

 is mated with a spotted mouse, and their self-colored offspring are mated together. 

 All the offspring of these crosses are mated to spotted mice. Assuming all matings 

 to be successful, and the resulting litters of equal size, what fraction of the mice from 

 the last matings should be spotted? 



23. Mating a red-eyed fly with curved wings and a claret-eyed fly with straight 

 wings yields an Fi all red-eyed and straight-winged. If the Fi flies are bred together 

 and produce 96 offspring, how many of these should be claret-eyed and straight-winged? 



24. Frizzled feathers in fowls are turned up at the end, smooth plumage lies down 

 flat. Pea and single combs are illustrated in Fig. 201. If a cross between single 

 smooth and pea frizzled yields pea frizzled, and if these are mated together and pro- 

 duce in the aggregate 48 fowls, how many of these should be single smooth? How 

 many pea frizzled? 



25. Self-colored rats (color distributed over the body) are dominant over hooded 

 (color only on head, rest of body white). Albino rat is recessive to gray. Crossing 

 a homozygous gray hooded rat with an albino having a pair of genes for self-color 

 (which, of course, cannot show in an albino) would produce what kind of offspring 

 in Fi? If the Fi animals were bred together and produced 80 offspring, how many 

 of these should be albino? How many gray hooded? 



26. Two walnut-combed fowls, mated together, produce 9 walnut-combed and 

 3 pea-combed ofifspring, and no others. Assuming that no class of offspring is missing 

 because of the small numbers, what were the formulas of the parents? 



27. In cattle, black (B) is dominant over yellow (fe), and polled (P) (hornless) is 

 dominant over horned (p). If several homozj^gous black horned cows are mated with 

 homozygous yellow hornless bulls, what will be the appearance of their offspring? 

 If these offspring are mated with one another, and in a number of such matings 9 

 yellow polled animals are produced, how many black polled ones would be expected? 

 How many yellow horned? 



28. If a homozygous red mule-footed pig (toes grown together) is mated with a 

 homozygous black normal-toed pig, their offspring are black and mule-footed. If 



