240 PRINCIPLES OF ANIMAL BIOLOGY 



to possess. Unfortunately, too little is known of the heredity of these 

 traits to raise the hope that such improvement is imminent. No one as 

 yet knows the formula for the production of genius at will. 



Problems 



1. A rose-combed fowl (Fig. 201, upper right) mated with a single-combed fowl 

 produces only rose-combed offspring. If many of these offspring are mated together 

 and produce an aggregate of 64 fowls, how many of the latter should be rose-combed? 



2. Tall peas are dominant over dwarf peas. What would be the appearance of 

 a plant heterozygous for tall and dwarf? If such a heterozygote were self-fertilized 

 and produced 30 dwarf offspring, how many tall offspring should it yield? 



3. Mating a red-eyed and a pink-eyed fly yields red-eyed offspring. If one of 

 these red-eyed offspring is mated with its pink parent, and they produce 60 offspring, 

 how many of these should be red-eyed? 



4. Brown color in mice is dominant over albinism. In a given cross between a 

 brown mouse and an albino, 6 of the offspring were brown, 5 albino. What was the 

 formula of the original brown parent? 



5. A long-winged fruit fly mated with one having vestigial wings (a recessive 

 character) produced 28 long-winged and 23 vestigial offspring. What were the 

 formulas of the parents? Of their long-winged offspring? Of their vestigial-winged 

 offspring? 



6. Snapdragons with bilaterally symmetrical flowers, crossed with plants with 

 radial flowers, produce only bilateral Fi. If an Fi plant is self-fertilized, what is the 

 chance that one of its offspring selected at random will be radial? 



7. Shepherd's-purse with triangular seed capsule is dominant over the variety 

 with spindle-shaped seed capsule. If a homozygous triangular is pollinated from a 

 heterozygous triangular, and 20 offspring are obtained from them, how many of these 

 should have spindle-shaped capsules? 



8. Starchy grain is dominant over sugary grain in corn. If, in a cross between 

 these types, 58 of the progeny are sugary, how many of the progeny should be starchy? 



9. A certain white-fruited squash, self-fertilized, produced some white and some 

 yellow offspring. If there were 21 yellows, how many white would be expected? 



10. Short hair is dominant over long hair in guinea pigs. A short-haired guinea 

 pig, one of whose parents was long-haired, was mated with a long-haired animal. 

 If, blindfolded, you selected one of their litter from the cage, what is the chance you 

 would get a long-haired animal? 



11. The offspring of a brown mouse and an albino are all brown. If the hetero- 

 zygous brown mice are mated together and produce 80 offspring, how many of these 

 should be albino? How many of the brown ones should be heterozygous? How 

 could you tell which browns were heterozygous? 



12. If gray color in an animal mutates to yellow, and in crosses between stocks 

 of gray and yellow the offspring are yellow, what (according to accepted conventions) 

 would be the symbol for the gray gene? For the yellow? 



13. If an animal having the formula Cc produces 100 eggs, how many of these 

 eggs should luive the formula C? How many c? How many Cc? 



14. A family consisting of 17 red-eyed and 15 purple-eyed flies probably came from 

 a mating of parents whose formulas were P and (Fill the blanks properly.) 



15. Applying the conventions relating to choice of symbols for genes, make a 

 number of matings between trotting horses Pp X Pp, and obtain 24 foals. How 

 many of these should be pacers? 



