A yeast strain that cannot grow in the absence of the amino acid histidine (his-) is mated with a yeast strain that cannot grow in the absence of the amino acid lysine (lys-). Among the 400 unordered tetrads resulting from this mating, 233 were PD, 11 were NPD, and 156 were TT. a. What haplotypes of spores are in the PD, NPD, and TT tetrads? (10 pts.) b. What is the distance in map units between the his and lys genes? (10 pts.) c. Assuming that none of these tetrads was caused by more than two crossovers between the genes, how can you estimate the number of meioses that generated these 400 tetrads in which zero, one, or two crossovers took place? Estimate the number.