You conduct a genetic screen on peas and isolate four mutant strains, each carrying a recessive mutation that causes the production of red peas (instead of the wild-type green peas).To test whether these mutations are in the same gene, you perform complementation tests between the four different true-breeding strains.The results from these complementation tests are shown in Table 19-33. $\begin{array} { c | c }
\text { Strains crossed } & \text { Phenotype of offspring } \
\hline 1 \times 2 & \text { green seeds } \
1 \times 3 & \text { green seeds } \
1 \times 4 & \text { red seeds } \
2 \times 3 & \text { red seeds } \
2 \times 4 & \text { green seeds } \
3 \times 4 & \text { green seeds }
\end{array}$ Table 19-33
Given this data, how many genes do these four alleles represent?

Question

You conduct a genetic screen on peas and isolate four mutant strains, each carrying a recessive mutation that causes the production of red peas (instead of the wild-type green peas).To test whether these mutations are in the same gene, you perform complementation tests between the four different true-breeding strains.The results from these complementation tests are shown in Table 19-33. $\begin{array} { c | c } 
\text { Strains crossed } & \text { Phenotype of offspring } \
\hline 1 \times 2 & \text { green seeds } \
1 \times 3 & \text { green seeds } \
1 \times 4 & \text { red seeds } \
2 \times 3 & \text { red seeds } \
2 \times 4 & \text { green seeds } \
3 \times 4 & \text { green seeds }
\end{array}$ Table 19-33
Given this data, how many genes do these four alleles represent?

Quizplus · Accepted Answer

The complementation tests show that mutations in strains 1, 2, and 3 can complement each other (as seen in the green seeds from crosses 1x2, 1x3, and 2x4), indicating they are in different genes. However, strain 4 does not complement any of the others (all crosses involving 4 result in red seeds when crossed with 1, but green seeds when 4 is crossed with 2 and 3), suggesting it is in the same gene as one of the others or represents a unique gene affecting the same pathway. Since strains 1, 2, and 3 can all complement each other but not strain 4, this suggests there are at least two genes involved: one gene represented by strains 1, 2, and 3, and another gene represented by strain 4.

You Conduct a Genetic Screen on Peas and Isolate Four