a.
To determine if the recessive suppressor mutation would suppress mutations in bli-4 or not, a dihybrid cross is to be done. The following shall be the genotypes of the gametes.
Let ‘B’ stands for the normal allele and ‘b’ for the recessive allele of bli-4 gene. The same way, let ‘S’ be the normal allele and ‘s’ be the mutant allele of the suppressor gene. They require worms of the genotype “Bb/Ss” to answer the questions.
b.
To make the worms of the genotype “Bb/Ss”, they require parents of the following genotypes:
• They are previously provided with a strain which is wild type and is recessive for suppressor mutation. Therefore, the genotype of this strain must be “BB/ss”
• The other strain to be chosen to perform the cross must be of the genotype “bb/SS” (mutant for bli-4 gene, and normal allele for the suppressor mutation)
c.
1. If the gene acted as a suppressor of bli-4, the expected dihybrid ratio of 13:3 in F2 generation (Thirteen wild type and three blistered)
2. 2. If the gene of interest did not act as a suppressor of bli-4, the expected dihybrid ratio is 12:4 (12 wild type and 4 blistered)