Definition of pachytene in US English:



  • The third stage of the prophase of meiosis, following zygotene, during which the paired chromosomes shorten and thicken, the two chromatids of each separate, and exchange of segments between chromatids may occur.

    • ‘This structural heterozygosity correlates with both a previously described recombination block and cytologically visible unpaired chromosomes at pachytene.’
    • ‘In addition, Creighton used pachytene stage chromosomes to continue deletion mapping studies.’
    • ‘Zygotene and pachytene chromosomes can be distinguished by their different morphology due to the extent of synapsis.’
    • ‘Homologous chromosomes are fully aligned at the pachytene stage, and germ cells survive to complete meiosis and gametogenesis with high efficiency.’
    • ‘During pachytene, the chromosomes are less condensed and much longer than in mitotic metaphases.’


Early 20th century: from Greek pakhus ‘thick’ + tainia ‘band’.