1. Linkage and Gene Maps
Remember that Mendel was lucky that all the traits he followed were controlled by genes on different chromosomes. Generally, genes that are on the same chromosome are inherited together; they are “linked.”
However, remember also that crossing over occurs during meiosis, this process may separate genes that are on the same chromosome.

2. The rate at which genes crossover can be used to map where a gene is located on a chromosome. The more frequent the rate of crossing over, the farther apart the genes are on a chromosome.

3. Note
Diploid = 2N
Haploid = N