Nonhomologous pairing in mice heterozygous for a t haplotype can produce recombinant chromosomes with duplications and deletions.
We have investigated the structure and properties of a chromosomal product recovered from a rare recombination event between a t haplotype and a wild-type form of mouse chromosome 17. Our embryological and molecular studies indicate that this chromosome (twLub2) is characterized by both a deletion and duplication of adjacent genetic material. The deletion appears to be responsible for a dominant lethal maternal effect and a recessive embryonic lethality. The duplication provides an explanation for the twLub2 suppression of the dominant T locus phenotype. A reanalysis of previously described results with another chromosome 17 variant called TtOrl indicates a structure for this chromosome that is reciprocal to that observed for twLub2. We have postulated the existence of an inversion over the proximal portion of all complete t haplotypes in order to explain the generation of the partial t haplotypes twLub2 and TtOrl. This proximal inversion and the previously described distal inversion are sufficient to account for all of the recombination properties that are characteristic of complete t haplotypes. The structures determined for twLub2 and TtOrl indicate that rare recombination can occur between nonequivalent genomic sequences within the inverted proximal t region when wild-type and t chromosomes are paired in a linear, nonhomologous configuration.
D000483:Alleles; D000818:Animals; D002872:Chromosome Deletion; D002874:Chromosome Mapping; D003434:Crossing Over, Genetic; D005804:Genes, Lethal; D005816:Genetic Complementation Test; D008040:Genetic Linkage; D006579:Heterozygote; D051379:Mice; D008817:Mice, Mutant Strains; D009154:Mutation; D010641:Phenotype; D011995:Recombination, Genetic