Final answer:
Crossing-over is the process during prophase I of meiosis where two separate events of chromosome breakage and exchange occur within the same tetrad, resulting in genetic diversity among gametes.
Step-by-step explanation:
The event describing two separate occurrences of chromosome breakage and exchange within the same tetrad during meiosis is known as crossing-over. This happens during prophase I of meiosis, when homologous chromosomes pair up gene-for-gene and form a tetrad, a unit of four chromatids. During crossing-over, chromosomal segments are exchanged between non-sister chromatids of these homologous chromosomes. This process can occur multiple times within the same pair of homologous chromosomes. The result is an exchange of genetic material, which contributes to the genetic diversity among gametes produced through meiosis. Such an exchange is pivotal for recombination and the formation of genetically unique offspring.