Chromosomes contain genes that determine an organism's traits and are passed down from parents to offspring. Meiosis is a type of cell division that produces sex cells like eggs and sperm, which each have half the number of chromosomes as body cells, ensuring offspring do not have twice the normal number when the parents' chromosomes combine during fertilization. Meiosis results in four sex cells with half the chromosomes of the original parent cell to maintain the chromosome number between generations.