[Synaptonemal complex analysis of 13/17 Robertsonian translocation in the domestic pig].

G and C-banding study of the chromosomes of several male pigs, indicate that all of these pigs carry rob(13;17). The karyotype is 2n = 37, XY, rob (13;17). In this paper, silverstained Synaptonemal Complexes (SCs) in surface-spread pachytene nuclei from these pigs are analysed by electron microscope. The result is as follows: Robertsonian translocation metacentrics rob (13;17) paired with homologous acrocentrics (13,17), forming a trivalent. All trivalents are in a cis configuration and there is delayed pairing in the trivalent. We measured every part of trivalent in the different stage of prophase (based on the morphology of XY-bivalent). It is shown that accompanying with rob(13;17) formation there has been a deletion in the proximal part of 13, 17 translocation chromosome. In the process of synapsis, the length adjustment phenomenon in the trivalent occurred: a. There is nonhomologous synapsis between the two short arms of the acrocentrics (13;17). The length of short SC varied. b. The position of the short SC, which is on the long SC(homologous synapsis of rob(13; 17) and 13, 17) moved, from one-fourth of long SC to one-tenth of it, near the end of 17 arm. These phenomenon is the result of a gradual length adjustment of lateral elements of 13,17 to the lateral element of the rob (13;17). We has discussed the mechanism of the trivalent synaptic adjustment, and it's important use to control the chiasmata and disjunction of the chromosomes.