Permanent Translocation Heterozygosity and Sex Determination in East African Mistletoes

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Science  28 Mar 1975:
Vol. 187, Issue 4182, pp. 1208-1209
DOI: 10.1126/science.187.4182.1208


Viscum fischeri has 2n = 23 chromosomes in male plants. These fornm 7 bivalents and a translocation chain of 9 chromosomes during meiosis. Pollen with 11-and 12-chromosome genomes is thus produced. Female plants have 2n = 22 chromosomes and produce 11 bivalents during meiosis. Sex determination is technically a rare multiple X-multiple Y type, but more importantly it provides the mechanism whereby permanent translocation heterozygosity is maintained in the system. In a second species, Viscum engleri, male plants have 2n=28 chromosomes associating as 11 bivalents and a ring of 6 chomosomes at meiosis.