International Mammalian Genome Society

The 13th International Mouse Genome Conference
October 31-November 3, 1999

Table of Contents * Structure * Bioinformatics * Sequence * Mapping * New Tools * Gene Discovery * Developmental * Mutagenesis * Functional Genomics

A2 Maternal Meiotic Drive at the Second Meiotic Division Caused by Unequal Segregation of Chromatids Carrying Different Alleles at the Om Locus

Fernando Pardo-Manuel de Villena, Elena de la Casa-Esperón, Tammi L. Briscoe and Carmen Sapienza. Temple School of Medicine, Philadelphia, Pennsylvania

We have shown previously that the progeny of crosses between (C57BL/6 x DDK) F1 females and C57BL/6 males show transmission ratio distortion at the Om locus in favor of the DDK allele. This result has been replicated in several independent experiments. Our results show that the distortion maps to a single locus on chromosome 11, closely linked to Om, and that gene conversion and inversions are not implicated in the origin of this phenomenon. To further investigate the origin of the transmission ratio distortion we generated a test using the well documented effect of recombination on maternal meiotic drive. The genetic test presented here discriminates between unequal segregation of alleles during meiosis and postfertilization lethality, based on the analysis of genotype at both the distorted locus and the centromere of the same chromosome. Using this test our results indicate that transmission ratio distortion at Om is caused by unequal segregation of chromatids carrying different alleles at Om to the polar body at the second meiotic division. Because the presence of segregation distortion at Om also depends on the genotype of the sire, our results confirm that the sperm can influence segregation of maternal chromosomes to the second polar body. Direct confirmation of the meiotic drive origin of the TRD was obtained by determining the allele present in both ova and second polar bodies in these crosses.


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