During meiosis crossing over gene exchange between chromosomes may occur. crossing over usually results in

Crossing over is also referred to as DNA recombination and occurs in prophase I of  meiosis I during cell divisions of sex cells. It is a process by while non-sister chromatids exchange their genetic materials. Crossing over is important in maintaining the genetic variations withing a given population of living organisms. since the composition of genetic material of offspring is different from that of their parents as result of crossing over, they may have some survival advantages not found in their parents.  

So they were repeated cause the actions were also repeated. See how it bounces back into the atomosphere twice.

Explanation:

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