Meiosis I starts with prophase I. Crossing over and independent assortment happens in prophase I. In crossing over, the same chromosomes are arranged by their chromatids and cross over the respective DNA. Genetic variation is produced because it results to several mixture of genes. Independent assortment happens during fertilization where zygote is produced. The gametes have varied set of DNA which makes a particular mixture of genes in the produced zygote. The chromosomes is the result of the separate split up of chromosomes to separate gametes.