Genetics: Analysis and Principles 5th Edition by Robert Brooker

Exercise 55

One yeast strain is lys + and arg + , whereas another strain is lys-3 and arg-2. The two strains were crossed to each other and an ascus obtained from this cross has four spores with the following genotypes: lys + arg + , lys + arg-2, lys-3 arg + , and lys-3 arg 2. This ascus is a
A) parental ditype
B) tetratype
C) nonparental ditype
D) could be b or c.