What does crossing-over contribute to in the process of meiosis?

Crossing-over is a vital process that occurs during prophase I of meiosis, where homologous chromosomes exchange portions of their chromatids. This exchange creates new combinations of alleles on each chromosome, which contributes significantly to genetic variation among offspring.

Genetic variation is essential for evolution and adaptation, as it enhances the diversity of traits within a population. When gametes are formed through meiosis, the combinations of alleles that result from crossing-over lead to genetically unique cells, ensuring that each individual produced has a distinct genetic makeup. This variation is a key factor in natural selection and contributes to the survival and adaptability of species.

In contrast, while cell growth, clonal reproduction, and reduction of chromosomes are processes related to cell division and reproduction, they do not directly result from crossing-over or pertain to the variation in genetic makeup that it facilitates.