How and where chiasma is formed?

Explanation

After tetrad formation, crossing over occurs in pachytene stage. The non-sister chromatids of homologous pair make a contact at one or more points. These points of contact between non-sister chromatids of homologous chromosomes are called chiasmata (singular-Chiasma). At chiasma, cross-shaped or X-shaped structure are formed, where breaking and rejoining of two chromatids occure. This results in reciprocal exchange of equal and corresponding segments between them.