388 INTRODUCTION TO EVOLUTION 



together. Considered alone, the mating of heterozygous black females to 

 heterozygous black males results in an expected % black offspring and 14 

 white (as with melanism in hamsters; see p. 379). Similarly, considered 



Black Short-haired {BbSs) 



Black Short-haired (BbSs) 

 OVA 



SPERMS 



BBSS 



BBSs 



BbSS 



13 



BbSs 



BBSs 



BBSS 



10 



BbSs 



14 



Bbss 



BbSS 



BbSs 



11 



bbSS 



15 



bbSs 



BbSs 



Bbss 



12 



bbSs 



16 



bbss 



Black 

 Short-haired 



Black 

 Long-haired 



(Nos. 1, 2, 3, 4,5, (Nos. 6, 8, 14) 

 7,9, 10, 13) 



Ratio 9 : 3 



"^JtM.. J 



White 

 Short-haired 



(Nos. 11, 12, 15) 



White 

 Long-haired 



(No. 16) 



FIG. 17.6. The effect of independent assortment of genes in determining the 

 offspring to be expected whein doubly heterozygous guinea pigs ore mated to 

 each other. 



alone, the mating of heterozygous short-haired females to heterozygous 

 short-haired males results in an expected % short-haired offspring and 

 ^ long-haired. Combining these expectations: 



