BIOL 102 Study Guide - X-Inactivation, Dna Ligase, Synaptonemal Complex
6 Jan 2014
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Document Summary
Formation of a bivalent and crossing over during meiosis i. at the beginning of meiosis, homologous chromosomes pair up to form a bivalent, usually with a synaptonemal complex between them. Crossing over occurs between homologous, nonsister chromatids within the bivalent. During this process, homologues exchange segments of chromosomes. For simplicity the two homologous chromosomes are shown side by side, with two nonsister chromatids close and two much farther apart. In real cells, however, the homologous chromosomes actually lie on top of each other; hence, both nonsister chromatids of homologous chromosomes are equivalent distances apart. The stages of meiosis in a plant cell. the top portion of each panel shows micrographs of nuclei of the easter lily (2n = 24) progressing through the indicated stages of meiosis. The lower panel gives a diagrammatic representation of the comparable event in a simpler nucleus (2n = 6).
