Chromosome interlocking during synapsis--a transient disorder.

The occurrence and resolution of chromosome interlocking have been monitored during chromosome pairing on 270 zygotene and 125 pachytene spread and silver stained chromosome complements from Bombyx spermatocytes. Interlockings form and resolve throughout zygotene. The estimated mean number of interlockings is 4.2 per nucleus at zygotene while only 3 presumptive interlockings were found in 125 pachytene nuclei. In individual zygotene nuclei up to 61% of the chromosomes are affected by interlocking. The mechanism for resolution of interlockings is discussed.