<P> Synapsis ( also called syndesis ) is the pairing of two homologous chromosomes that occurs during meiosis . It allows matching - up of homologous pairs prior to their segregation , and possible chromosomal crossover between them . Synapsis takes place during prophase I of meiosis . When homologous chromosomes synapse , their ends are first attached to the nuclear envelope . These end - membrane complexes then migrate , assisted by the extranuclear cytoskeleton , until matching ends have been paired . Then the intervening regions of the chromosome are brought together , and may be connected by a protein - RNA complex called the synaptonemal complex . Autosomes undergo synapsis during meiosis , and are held together by a protein complex along the whole length of the chromosomes called the synaptonemal complex . Sex chromosomes also undergo synapsis ; however , the synaptonemal protein complex that holds the homologous chromosomes together is only present at one end of each sex chromosome . </P>
when does synapsis of homologous chromosomes occur in mitosis
during prophase I of meiosis