Homologous chromosomes pair along their length during prophase I of meiosis. While two homologues are paired, genetic exchange may occur between them in a process called .

Crossing over

Explanation:

The onset of meiosis is characterized by shortening and thickening of genetic materials to form visible threads. Thereafter, homologous chromosomes pair up to a 4-chromosome structure known as tetrad.

The paired homologous chromosome then go ahead to exchange portions of chromosomes in a process known as crossing over of genetic materials.