Progress through m eiosis M ole cular interact ion 14.2 Breakage and Leptotene M Each chrom osome has chrom somes become Sible, often Ba Oreplicated,andonsistsof 2 sister chromatids reunion involves etched to nuc A Mv heteroduplex dna Chromosom es begin AM Intiation pairing in lim ited Figure 14.1 Recombination occurs region or regions NN during the first meiotic prophase The stages of prophase are defined Pachytene by the appearance of the Synaptonem al /A Strand exchange complex extends vA Single strands exchange chromosomes. each of which along entire length of paired chromosomes A MVM consists of two replicas(sister chromatids), although the Chromosom es Nv Assimilation duplicated state becomes visible separate but are held Region of exchanged MM strands is extended only at the end. The molecular chiasmata 及 AA interactions of any individual crossing-over event involve two of Cibimoson AV Resolution the four duplex dnas condense. detach AWV from envelope chromatids become 消当Figure 14.1 Recombination occurs during the first meiotic prophase. The stages of prophase are defined by the appearance of the chromosomes, each of which consists of two replicas (sister chromatids), although the duplicated state becomes visible only at the end. The molecular interactions of any individual crossing-over event involve two of the four duplex DNAs. 14.2 Breakage and reunion involves heteroduplex DNA