Question

What two essential criteria must be met in order to execute a successful mapping cross?

Short answer

Answer: The two essential criteria for a successful mapping cross are: 1) the organisms being crossed must be pure-breeding or true-breeding for the traits being studied, and 2) the traits being studied must be linked, meaning they are inherited together more often than expected by chance due to their proximity on the same chromosome.

Step-by-step solution

1. Pure-breeding organisms

In a successful mapping cross, the organisms being crossed must be pure-breeding, or true-breeding, for the traits being studied. This means that these organisms consistently pass down their traits unchanged to their offspring, ensuring that the genes contributing to those traits are homozygous. This ensures clear and consistent inheritance patterns in F1 and F2 generations, which are crucial for making accurate predictions and conclusions about the inheritance of the traits being studied.

2. Linked traits

The second essential criterion for a successful mapping cross is that the traits being studied must be linked. This means they are located close to each other on the same chromosome, causing them to be inherited together more often than expected by chance as there is a lower probability of crossing over occurring between them during meiosis. As a result, the recombination frequency between linked traits is less than 50%. By analyzing the recombination frequency, the distance between the linked traits can be determined and the order of the genes on the chromosome can be mapped.