Genetic linkage is when genes that are close together on the same chromosome are inherited together.
Normally, genes separate and assort independently during meiosis, but if two genes are very close to each other, they tend to stay linked and move together into the same gamete.
This happens because crossing over, which swaps parts of chromosomes, is less likely to occur between genes that are very close. The closer the genes are, the stronger their linkage.
As a result, the usual Mendelian ratios may not appear because some combinations of traits are passed on together more often than others.
For example, in maize, genes that control seed color and texture may be linked, so certain trait combinations appear more frequently in offspring.
Each chromosome forms a linkage group that includes many linked genes. The number of linkage groups in a plant equals its number of chromosomes.
Sometimes, crossing over can break the linkage and create new combinations of traits. The more often this happens, the farther apart the genes are on the chromosome.
Genetic linkage is important because it helps explain why some traits are inherited together. It is also used in genetic mapping to locate genes and in plant breeding to combine useful traits like disease resistance and high yield.