Final answer:
A crossing over event in meiosis that involves the exchange of chromosomal material between sister chromatids is known as recombination, which occurs during prophase I and results in genetic diversity.
Step-by-step explanation:
A crossing over event in meiosis or mitotic cells involving the reciprocal exchange of chromosomal material between sister chromatids joined by a centromere is referred to as a recombination. During prophase I of meiosis, homologous chromosomes line up and form a tetrad. The chromatids are very close to each other and the exchange of genetic material, or crossover, occurs. This reciprocal exchange happens between non-sister chromatids and results in chromosomes that carry genetic information from both parents, creating unique combinations of genes.
Crossover is a key mechanism in generating genetic diversity. It occurs between the non-sister chromatids of homologous chromosomes with the result being an exchange of genetic material between the chromosomes. This is observable as chiasmata under a microscope. Each crossover event results in recombinant chromosomes, which combine DNA from both parents, contributing to genetic variation in offspring.