PRINCIPLES OF HEREOnY 



659 



the phenotypes o£ the parents and, if necessary, from the phenotypes 

 of the offspring. 



3. Derive all of the possible types of gametes each parent would 

 produce. 



4. Prepare the appropriate Punnett square and write the possible 

 types of eggs across its top and the types of sperm along its side. 



5. Fill in the squares with the appropriate genotypes and read off 

 the genotypic and phenotypic ratios of the offspring. 



As an example of the method of solving a problem in genetics, let 

 us consider the following: The length of fur in cats is an inherited 

 trait; the gene for long hair (I), as in Persian cats, is recessive to the gene 

 for short hair (L) of the common tabby cat. Let us suppose that a short- 

 haired male is bred to three different females, two of which, A and C, 

 are short-haired and one, B, is long-haired (Fig. 32.3). Cat A gives birth 

 to a short-haired kitten, but cats B and C each produce a long-haired 

 kitten. What offsj^ring could be expected from further mating of this 

 male with these three females? 



Since the longhaired trait is recessive we know that all the long- 



00 



Cat A, short-haired 



Short -haired Kitten 



Short-haired mr le caJb 



00 



Cats, long-h.cLxrzci 



m 



Long-haired Kitten 



00 



Ca-tC, short-haired 



00 



Lorjg-haired kitten. 



Figure 32.3. An example of problem-solving in genetics: deducing parental geno- 

 types from the phenotypes of the ofEspring. See text for discussion. 



