Mapping Recombination Nodules on Synaptonemal Complexes of Maize

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9728673 Stack An analysis of recombination nodules (RNs) on synaptonemal complexes (SCs) will be used to determine the pattern of crossing over in KYS maize. Because each RN reliably marks the position of a genetic crossover event, mapping RNs on SCs is a high-resolution method to examine the frequency and distribution of crossing over on each bivalent of an entire set of chromosomes without dependence on saturation or terminal markers. A standard karyotype for maize SCs will be prepared and each SC on the basis of relative length and arm ratio will be identified and then related to a specific chromosome by examining inversion heterozygotes for each of the ten chromosomes of maize. An examination of 450-500 normal SCs of each type will allow a detailed map of the distribution and frequency of RNs along each of the ten maize SCs to be prepared. The data will be used to analyze crossing over in regard to hot and cold spots, interference within and between arms and chromosomal features such as telomeres, kinetochores, and heterochromatin. As an ancillary project, the influence of inversion heterozygosity on crossover suppression and interference within and between chromosomes, the Schultz-Redfield effect, will be investigated. A more limited examination of the distribution of RNs in teosinte, the wild progenitor of maize will be done. Several varieties of maize (TX303, CO 159, B73 and NO17) that have been used to prepare the molecular linkage map for maize, (as well as some that are important for breeding programs), will be used as test strains to determine the general applicability of the method before a strain is chosen for a complete analysis. An RN map for maize will be a physical map of recombination that will complement the existing gene and molecular linkage maps for maize and, as such, will be of importance in a genomic approach to both basic studies and breeding programs.