338 Interaction of Genes 



QUESTIONS AND PROBLEMS 



1. Give the phenotypes of the following crosses made between plants 

 of Oenothera Lamarckiana: 



(a) Ss Vv X ss vv (d) Ss Vv X ss VV 



(b) Ss Vv X Ss VV (e) Ss Vv X SS vv 



(c) Ss Vv X SS Vv (/) Ss Vv X Ss Vv 



2. In poultry, what are the results obtained from crossing a walnut- 

 combed Fi fowl with (a) a pure-bred pea, (b) a pure-bred rose, and (c) a 

 single? What are the offspring from crossing a single with (a) a heterozy- 

 gous rose and (6) a heterozygous pea? 



3. In rats, gene C produces a pigmented coat, whereas c produces an 

 unpigmented or albino coat. Genes A and R interact to produce gray 

 fur; A with homozygous r results in yellow; aa with R produces black; 

 aa rr animals are cream. These four coat colors, however, are found only 

 if C is also present. What are the results of the following crosses? 



(a) CC Aa Rr X CC Aa Rr (c) CC Aa Rr X CC Aa rr 



(b) CC Aa Rr X CC aa Rr (d) CC Aa Rr X CC aa rr 



4. Give the phenotypes of the offspring of the following rat crosses 

 (see problem 3) : 



(a) CC aa Rr X cc aa Rr (/) CC Aa rr X cc Aa rr 



(b) Cc aa Rr X Cc aa Rr (g) Cc Aarr X Cc Aa rr 



(c) Cc aa Rr X cc aa Rr (h) Cc Aa rr X cc Aa rr 



(d) Cc aa rr X Cc aa Rr (i) Cc aa rr X Cc Aa rr 



(e) cc Aa Rr X cc Aa Rr 



5. In flax, two blue-flowered plants were crossed, and the offspring 

 segregated into 65 blue, 20 lilac, and 27 white. What were the genotypes 

 of the parents? 



6. In the summer squash, gene W produces white and gene w colored 

 fruit. Gene Y if combined with ww colors the fruit yellow, whereas 

 vrw yy plants have green fruit. What are the phenotypes and genotypes 

 of the offspring of the following crosses? 



(a) WW YY X Ww yy (d) Ww ijy X ww Yy 



(6) Ww Yy X Ww Yy (e) WW yy X ww YY 



(c) Ww Yy X low yy 



