C-band fusion and behaviour of the involved chromosomes during meiotic prophase I of the male domestic pig

Abstract

Behaviour of acrocentric chromosome synaptonemal complexes (SCs) and constitutive heterochromatin (C-band) during meiotic prophase I of the male domestic pig was studied using surface spreading and silver staining techniques. At late zygotene C-band regions of complete or incomplete SCs of the acrocentric chromosomes are represented by enlarged structures. At the same time these structures commenced fusion, which is accomplished at pachytene. Using kinetochores and NORs as markers, the pachytene metacentric, acrocentric, and nucleolar SCs can be distinguished. In 96.7% of the pachytene nuclei, either all or some of the acrocentric SCs are associated at their centromeric regions, forming one or two large globular or shapeless masses that represent chromocenters. The SCs are assorted at random in all types of association except in single association of all the SCs. Order of associated SCs varies from one association to another. The C-band region of SC, the portion inside the chromocenter core, is differentiated as thicker and darker structures from the chromocenter mass. A silver-positive core-like structure in meiotic chromosome C-bands, probably a vector for meiotic C-band ectopic pairing, provides faithful representations of C-band behaviour during meiosis.