To focus more on the offspring and how it results in the formation of the f1 generation, is an inheritance called sex-linkage,[3] which is a gene which is located on the sex chromosome and patterns of these inheritance differ in both male and female. The explanation that proves the theory of the offspring having genes from both parent generations, is proven through a process called crossing-over, which consists of taking genes from the male chromosomes and genes from the female chromosome, resulting in a process of meiosis occurring, and leading to the splitting of the chromosomes evenly.[4] Depending on which genes are dominantly expressed in the gene will result in the sex of the offspring. The female will always give an X chromosome, whereas the male, depending on the situation, will either give an X chromosome or a Y chromosome.