Crossing over involves which mechanism during meiosis?

Crossing over is a crucial mechanism that occurs during meiosis, specifically during prophase I. It involves the swapping of DNA segments between homologous chromatids, leading to genetic recombination. This process ensures that the resulting gametes have a unique combination of genes, which contributes to genetic diversity in offspring.

During crossing over, homologous chromosomes pair up and exchange segments of their genetic material. This exchange can occur at various points along the chromosomes and effectively reshuffles the alleles between the two chromosomes, which is essential for evolution and adaptation in populations. The contribution of crossing over to genetic variation is significant, as it allows for new combinations of traits in the offspring.

The other mechanisms listed in the choices do not pertain to crossing over. The random assortment of chromosomes refers to the way chromosomes are distributed into daughter cells independently during metaphase I of meiosis. The replication of DNA happens before meiosis begins, ensuring each chromosome is duplicated before the process of division. Lastly, the alignment of chromosomes occurs during anaphase, where sister chromatids are pulled apart, but this process does not involve any exchange of genetic material. Thus, the specific nature of crossing over as the swap of DNA segments between homologous chromatids is what makes this the correct