Every pair of homologs acquires at least one crossover and chiasma. When 2 or more events occur along a chromosome, they exhibit interference: if an event is present at one position, there is a reduced probability that another event will be found nearby. Interference is maximal at short distances and decreases progressively with increasing distance between positions.

The synaptonemal complex (SC) is usually present in early prophase I. The SC is a tripartite fibrous ladder that holds sister chromatids together.