Date of Award

10-1-1995

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology

Abstract

A collection of stocks has been developed in which the variegated allele (P-vv) of the pericarp color locus (p1) has been brought into coupling with much of the maize genome using pericentric inversions and reciprocal translocations. These stocks now make most of the maize genome accessible to insertional mutagenesis by the transposable element Activator (Ac) originating from P-vv. The p1 locus is on the short arm of chromosome one (IS). The collection includes five stocks with chromosome one pericentric inversions and 45 stocks with reciprocal translocations involving 1S. The inversion and translocation stocks were converted through genetic recombination so that the inversion or translocation chromosome possesses the Ac bearing P-vv allele at the p1 locus. Each stock has the P-vv allele containing 1S segment coupled to a different chromosomal region. In transposing, the Ac element favors reinsertion sites that are linked to the excision site. These chromosomal regions are then more susceptible than unlinked regions to Ac insertions originating from P-vv.For several of the reciprocal translocation stocks, the location of their breakpoints were analyzed by genetic recombination experiments. A notable feature of the data presented was that, in many cases, there was an excess of observed double crossovers progeny relative to what would be expected from the recombination values of the involved intervals. An excess of double crossovers caused the coefficient of coincidence to exceed one (negative interference). Excessive values of this statistic can result in both an incorrect determination of locus order and in the placement of the translocation breakpoint relative to the other loci. It is unclear what the basis is of these high coefficient of coincidence values.

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