The diagram given below represents a certain phenomenon which occurs during meiosis. Name and explain the phenomenon by using the terms - homologous chromosomes, chromatids, crossing-over.

In the first meiotic division, homologous chromosomes come close together to form a pair called a bivalent. A bivalent has two chromosomes, one paternal and one maternal. The pairing of homologous chromosomes is known as synapsis. During pairing, some chromatids of homologous chromosomes break and rejoin at points of intersection, called chiasmata. This causes crossing over with exchange of chromatid segments between the two chromosomes of a homologous pair. It leads to the formation of new gene combination in the resulting chromosomes.