Questions and Problems 145 



24. Assume that an organism is heterozygous for six pairs of genes, 

 (a) How many different kinds of gametes does it produce? (6) How 

 many different kinds of phenotypes are produced on selfing? (c) How 

 many different kinds of individuals are found in the offspring of the test- 

 cross of that organism to an organism recessive for all six genes? (d) 

 How many different kinds of genotypes are produced if this organism is 

 selfed? (e) What is the smallest theoretical number of individuals re- 

 quired to get an individual recessive for all six genes if this organism is 

 selfed ? 



25. In Capsella, genes A and B determine leaf shapes (see problem 8) ; 

 gene v produces fasciated stems and is recessive to V, the gene for non- 

 fasciated stems. What are the phenotypes of the offspring from the fol- 

 lowing crosses? 



AA Bbvv X aa bb VV 



Aa Bb VV X aa bb vv 

 Aa bb VV X aa Bb Vv 



26. What are the phenotypes of the F^ from the following crosses 

 (assume all parents to be homozygous) : 



tenuis nonfasciated X rhomboidea fasciated 

 heteris nonfasciated X simplex fasciated 

 tenuis fasciated X rhomboidea nonfasciated 

 tenuis fasciated X simplex nonfasciated. 



27. Plant AA BB CC was crossed with aa bb cc. The F2 segregated 

 into bo7ABC : 189^5c : imAbC : ISiaBC : 58Abc : maBc : 62abC : 

 19abc. Calculate x^ and the probability that this is a true trihybrid 

 ratio. 



28. In Nemesia strumosa, colored (C) is dominant to colorless (c), 

 orange (0) is dominant to white (0), and mark {m} on the lower lip 

 is recessive to no mark (M). A family of plants of unknown parentage 

 produced the following plants: 91 colored, orange, nonmarked : 88 col- 

 ored, orange, marked : 29 colored, white, nonmarked : 30 colored, white, 

 marked : 31 noncolored, orange, nonmarked : 28 noncolored, white, 

 marked. What are the genotypes of the parents? 



29. What are the offspring of the following crosses (see question 28 j ? 



Cc Oo Mm X CC Oo mm 

 Cc Oo Mm X cc 00 mm 

 Cc Oo Mm X cc 00 Mm 



