Genetic recombination is the rearrangement of genes to produce offspring with different combinations of traits than either parent. Recombination is the source of genetic diversity in sexually reproducing organisms.
During prophase I of meiosis, the creation of sex cells, pairs of chromosomes from each parent line up in close contact with one another. Sometimes, maternal and paternal chromosomes cross over, and this area of contact is a chiasma. Eventually, the chiasma breaks and sections of the chromosome trade from one to the other. This event creates sex cells with different gene combinations than the parent chromosomes.
Some genes lay very close together on a chromosome and are less likely to switch during a crossing over event; these are linked genes. Depending on their closeness, linked genes have a high likelihood of inheriting together. One common example of linked genes is red hair and freckles. Freckles are an anomaly in skin pigmentation due to the MC1R gene. This gene sits close the gene that codes for red hair, meaning that they tend to stick together and resist crossing over.
If the chromosome pieces that cross over are not like, or homologous, sections, a translocation mutation occurs. Translocation mutations sometimes cause cancerous cells to arise.