V. GENE LIST AND WORKING MAPS

 


Following is the current genelist, arranged by gene symbol, identifying the unit factors for which stocks are available in the Maize Genetics Stock Center (Department of Agronomy, University of Illinois, Urbana, Illinois 61801), those for which variants exist in generally available strains (e.g. isozyme variants), and those upon which current or recent research studies have been published or have been reported in the Maize Genetics Cooperation Newsletter. The information tabulated includes the chromosome (L=long arm, S=short arm) and map position or approximate position, the name and phenotype, availability from the Stock Center (S), a photograph (P) in the Mutants of Maize (Neuffer, M.G., et al. 1968, Crop Sci. Soc. Amer., Madison, WI), and references to the original descriptions.

Following the gene list are the current working maps for each chromosome. The traditional linkage map based on conventional factors and isozymes is presented in the center. Each linkage map represents the order and recombinational distances, in centimorgans (1% recombination = 1 cM), for those genes for which sufficient information is available to make a reasonable judgment of their location. Each chromosome is arranged beginning with the most distal gene in the short arm. Locations of the centromeres are indicated according to the best available data from cytogenetic studies. The physical map of each chromosome, immediately to the left of each linkage map, is drawn with the length of each arm in proportion to the ratio of the length of that arm to the length on chromosome 1. Locations of the B-A translocations, which generate hemizygous segments, are shown as TB-...; placement on the physical map is in accordance with observed breakpoints; placement on the linkage map is in relation to genes uncovered or not uncovered. The vertical line associated with simple B-A translocations represents the segment within which the breakpoint is located (genes distal to the line on that arm should be uncovered). In the case of compound translocations, the associated vertical line on the linkage map for the first arm involved (e.g., 1L of TB-1La-5S8041) defines the segment within which the second breakpoint is located (genes distal to the line are not uncovered). On the map of the second arm involved (5S, in the example), genes distal to the associated line are uncovered (as they are with simple B-A translocations). TB's shown spanning one or more genes may or may not uncover the indicated gene or genes. Immediately to the right of the linkage map are those genes that have some information leading to a "rough" placement on the map, either near a gene already on the map or to a region of the map. Further to the right are those genes which have been only placed to chromosome (represented by the vertical line with arrows at both ends) or to one arm (represented by a vertical line running from near the centromere to the end of the arm).

To left of each chromosome's physical map are the current versions of the public restriction fragment length polymorphism (RFLP) maps developed by B. Burr at the Brookhaven National Labs (on the left) and D. Hoisington at the University of Missouri (on the right). On the right of the Missouri map are preliminary localizations of conventional markers based on work at Missouri and that provided by other researchers. The horizontal ticks indicate the RFLP loci used in mapping the gene or genes.

The Integrated Mapping Project, developed under the encouragement, advice and efforts of the maize community, is in the second of 3 years of funding from NSF. The focus of the prioritized work under this support is (1) to set a universally usable framework of RFLP markers; (2) to define physical locations with B-A and A-A translocations; and (3) to map a selected group of conventional markers (see notes in this Newsletter). It is important to stress that this effort in no way decreases the need for others to map (either traditionally or with RFLPs). What this project will do is provide a means by which these data can be assembled and distributed to all interested research workers.

The importance of placing loci defined by probes of known function cannot be overstressed. In a number of cases these provide very accurate ties to the conventional map and, in the very least, provide functional significance to a particular region of the genome that will be important as further additional studies (particularly in the area of quantitative genetics) progress. Therefore, if you have a clone for a known function and know or believe that it hybridizes to a maize genomic sequence, please attempt to map the locus (or loci). This can be accomplished in a couple of ways (and we recommend doing both). First, the set of recombinant inbreds should be probed and the data sent to Ben Burr for analysis. Secondly, it would be appreciated if the probe could be sent to Missouri for mapping in F2 and testcross populations. We would also be able to use the probe in our correlation to physical and conventional markers. We have included in this Newsletter a sample form of the desired information for each clone you provide. If you have any questions regarding mapping of RFLP loci (both old and new), please call or write.

As usual, any comments and/or changes to the maps are greatly appreciated.

Ed Coe, Dave Hoisington and Shiaoman Chao


Please Note: Notes submitted to the Maize Genetics Cooperation Newsletter may be cited only with consent of the authors

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