Final answer:
During meiosis, homologous chromosomes pair tightly in a process called synapsis, facilitated by the synaptonemal complex, which also enables crossing over for genetic variation.
Step-by-step explanation:
During meiosis, homologous chromosomes become closely associated in the process of pairing or also referred to as synapsis. This pairing occurs during prophase I of meiosis, where the chromosome pairs are held together by a protein lattice known as the synaptonemal complex. The synaptonemal complex not only aligns the homologous chromosomes perfectly but also supports crossing over, an essential process for genetic variation. Crossing over involves the exchange of chromosomal segments between non-sister homologous chromatids, leading to new combinations of genes.
As the nuclear envelope begins to break down, the synaptonemal complex forms, eventually covering the entirety of the chromosomes. The tight pairing of the homologous chromosomes allows for the precise alignment of genes. Following the crossover events, the homologous chromosomes remain attached at the locations of these crossovers, known as chiasmata, and are visible as tetrads, consisting of four sister chromatids.