Final answer:
The pairing of homologous chromosomes during meiosis is known as synapsis, leading to crossing-over during prophase I which contributes to genetic diversity in offspring.
Step-by-step explanation:
The pairing up of homologous chromosomes during meiosis is called synapsis. This critical process occurs during prophase I of meiosis I, where homologous chromosomes come close together and align precisely with one another. The formation of a synaptonemal complex between chromosomes supports the exchange of genetic material in a process known as crossing-over. Crossing-over leads to the generation of new combinations of genes on each chromosome, contributing to genetic diversity in offspring.
This pairing and recombination are essential as they ensure that gametes (sex cells) receive a mix of maternal and paternal genes, rather than a direct copy from either parent. As a result, the synaptonemal complex not only assists in the physical connection of chromosomes but also facilitates the precise alignment of genes for successful crossover events, visible after the exchange as chiasmata.