Final answer:
During prophase I of meiosis, homologous chromosomes form tetrads. Tetrads are formed when two duplicated homologous chromosomes pair up and become connected by structures called chiasmata.
Step-by-step explanation:
During prophase I of meiosis, homologous chromosomes form tetrads. Tetrads are formed when two duplicated homologous chromosomes, each consisting of two sister chromatids, pair up and become connected by structures called chiasmata. This pairing and formation of tetrads allow for genetic recombination between homologous chromosomes, leading to genetic variation in offspring.