Cell Cycle and Cell Division — BIOLOGY STD 11 Science — Question

The synaptonemal complex is a tripartite, ribbon-like structure, and is sihiated between pairing homologous chromosomes. It consists of a dense central element, with a dense lateral element on either side. Each lateral element is attached on the inner side of a homologous chromosome. The space between the central and lateral elements is traversed by a series of transverse units of LC fibres (L for lateral and C for central), which connects the two. The synaptonemal complex is attached at both ends through its lateral elements to the inner surface of the nuclear membrane. The central element is not attached directly. Also arising from the lateral elements is another series of smaller loops. These loops fuse in the middle line to make up the central element. The transverse parts of the loops form the transverse units or LC fibres. The central element is simple in some organisms (e.g., frogs and mice) and tripartite in other (e.g., insects). Each lateral element consists of two protein filaments, one for each sister chromatid. Synaptonemal complex first appears during zygotene.