In chromosomal crossover, genetic exchange increases variation because the genes recombine to form another gene that is new. Only during phase 1 of meiosis, can the similar traits of the chromosome unite, making a variation. The farther apart the common traits of the chromosome are, the more likely variation will occur.
When eggs and sperm unite, they form chromosomes. People each have 23 pairs of chromosomes. When each pair divides during meiosis, they can join to another half of chromosome from either the egg or the sperm. To become pairs, two parts from different chromosomes press together and sometimes break. The broken piece can then join with another broken piece and thus become a separate cell that differs from the original chromosome. Each piece has specific genetic information that makes the person have different traits. Often, those traits are very different from the parents.
Sometimes genes called linked genes do not separate. This often happens with diseases. Geneticists call them a "marker".
These cells then match up with sex cells to determine the person's sex. These move separately and freely in a process known as independent assortment.
By identifying where on the chromosome the different traits lie, scientists can make different things happen. The color of a flower and the length of a dog's leg can change in meiosis with the help of a scientist to create the genetic variation.
Genetic crossover opens doors to having more healthy crops and livestock. Once scientists know where to manipulate a chromosome then the variations become limitless.
Genetic crossover also opens doors in preventing or helping people with various diseases. By changing the cell that causes the disease, the effects of the disease diminish.
If the chromosomes rejoin incorrectly, serious problems can occur like Down's syndrome or miscarriages. This happens because the cell has one less chromosome with which to grow.
In a 2008 study relating to the health and inheritance of the Hutterites by Carole Ober, PhD at the University of Chicago found that older woman had more chromosomal crossover as they aged than younger women. Age had no effect on the male's chromosomes. The researchers used 500,000 markers to arrive at their conclusions. This study showed much variation over many parts of the chromosomes. In the future, the researchers hope to extend the study to understand the rate that recombination occurs. The Hutterities are a group of European immigrants living in the Dakotas. They are a community of agriculturalists.