by what the synaptonemal complex is made of?  what are its functions?

Synaptonemal complexes (SCs) are zipper-like protein structures that are formed between homologous chromosomes during the prophase of the first meiotic division. It stabilizes the pairing of homologous chromosomes (synapsis) and promotes crossing over. SCs are used to detect the abnormalities in pairing in case of individuals who are suffering from chromosomal abnormalities (either in chromosome number or structure).