A stably transmitted pair of translocated supernumerary chromosomes in maize

A pair of stably transmitted supernumerary chromosomes of unknown source has been found in a maize stock carrying a desynaptic mutant. The presence of the supernumerary chromosome appears to be unrelated to the meiotic mutant, but is believed to have been derived from a translocated B chromosome contaminant. The supernumerary chromosomes carry a segment of a A chromosome in this stock where there appear to be two normal copies of each of the 10 A chromosomes. Thus, this A chromosome segment is present in quadruplicate. Surprisingly, a quadrivalent configuration is formed in most microsporocytes, which involves not only synapsis but also chiasma formation in the A chromosome segments involved in the quadrivalent. This represents a strong preferential pairing of supernumeraries with the normal A chromosome segments. Such nonrandom association and crossing over might provide information on the nature of early homologue alignment at meiosis.