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How does crossing over during meiosis create new gene combinations?

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Four kittens with different fur patterns-three tabby and one black-and-white-lying together in a box, illustrating genetic variation among offspring. — heredity Each offspring is a combination of its two parents, receiving some dominant traits from its mother and others from its father.

During meiosis, crossing over creates new gene combinations by facilitating the exchange of genetic material between homologous chromosomes.12

The process occurs during prophase I, when homologous maternal and paternal chromosomes pair closely to form a tetrad, consisting of four chromatids. At this stage, corresponding segments of the maternal and paternal chromosomes are exchanged. This physical breakage and reunion of homologous chromosomes disrupts existing linkage groups, resulting in chromatids that contain a unique mixture of both paternal and maternal genes.2314

Because of this exchange, the resulting gametes are not genetically identical to the parent cell or to each other. This mechanism ensures constant genetic variability, as the final haploid cells contain chromosomes that are new combinations of the genes present in the original diploid cell. This process is fundamental to heredity, as it demonstrates that genes, rather than entire chromosomes, are the primary units of inheritance.123