The farmer can use variation in the height of the corn plants to cross them and produce taller corn plants. The farmer's work will be most effective if height is determined by codominance.
Codominance refers to the fact that different alleles of a given gene locus can affect a phenotype.
The farmer's work will be most effective if height is determined by codominance because he/she will need to select hybrid plants in a generation to breed them.
The farmer can observe the proportion of taller offspring that are affected by the disease in order to analyze if heigh and disease resistance genes are linked.
If these genes are linked, then it is required to cross plants and then select recombinant offspring with desired features (in this case, taller and disease resistance plants).
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