, Volume 190, Issue 1, pp 117-121

Unequal crossing-over between yeast transposable elements

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Summary

I have detected crossing-over between transposable elements at different sites on homologous yeast chromosomes. The recombination events described here involve a Ty element, called Ty917, near the HIS4 locus and a Ty element, known as Ty1-17, near the LEU2 gene. Ty917 and Ty1-17 lie in the same orientation on chromosome III and they are separated by approximately 21 kilobase pairs of DNA. Reciprocal recombination between the Ty917 element on one chromosome and the Ty1-17 element on the homologous chromosome in a diploid yeast cell results in the production of two aberrant chromosomes. One of these carries a deletion of the region between HIS4 and LEU2 and the other carries a duplication of this segment of DNA. The unequal crossover events have been demonstrated by genetic analysis of strains carrying the recombinant chromosomes and by cloning and restriction mapping of the novel junction fragments generated by recombination between Ty elements. Unequal crossing-over between Ty917 and Ty1-17 occurs in more than 1% of diploid yeast cells undergoing meiosis. Recombination between Ty917 and Ty1-17 occurs in less than 10-7 haploid cells dividing mitotically.

Communicated by G. Fink