Integrated linkage maps in the rat.
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Biomedical subjects
K K Levan
Publications and source records attributed to K K Levan.
Universal mapping probes and the origin of human chromosome 3.
Universal mapping probes (UMPs) are defined as short segments of human DNA that are useful for physical and genetic mapping in a wide variety of mammals. The most useful UMPs contain a conserved DNA sequence immediately adjoined to a highly polymorphic CA repeat. The conserved region determines physical gene location, whereas the CA repeat facilitates genetic mapping. Both the CA repeat and its neighboring sequence are highly conserved in evolution. This permits molecular, cytogenetic, and genetic mapping of UMPs throughout mammalia. UMPs are significant because they make genetic information cumulative among well-studied species and because they transfer such information from "map rich" organisms to those that are "map poor." As a demonstration of the utility of UMPs, comparative maps between human chromosome 3 (HSA3) and the rat genome have been constructed. HSA3 is defined by at least 12 syntenic clusters located on seven different rat chromosomes. These data, together with previous comparative mapping information between human, mouse, and bovine genomes, allow us to propose a distinct evolutionary pathway that connects HSA3 with the chromosomes of rodents, artiodactyls, and primates. The model predicts a parsimonious phylogenetic tree, is readily testable, and will be of considerable use for determining the pathways of mammalian evolution.
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New markers, D16FC1 and Tp12, differentiate between rat chromosomes 16 and 17.
Problems in differentiating rat chromosomes 16 and 17 cytogenetically can be resolved with unique probes mapped to these chromosomes. Using somatic cell hybridization and nonisotopic in situ hybridization, probes D16FC1 and Tp12 were localized to 16p16-->p15 and 17q12.1-->q12.2, respectively. The locations of these probes can serve as reference points to facilitate mapping of future probes to rat chromosomes 16 and 17.
Animals↗
Measuring genome reorganization from synteny data.
Two measures of the degree of genome reorganization based on synteny data are presented. The first, q, measures how far the original syntenic relationships have decayed during the separation of two taxa. The second measure, Q, is a logarithmic transformation of q, so constructed that Q increases unlimitedly while q deflects when reorganization becomes substantial. Numerical examples are given for the genomic reorganizations that have occurred during the evolution of humans, mice and rats. The degree of genome reorganization between the mouse and the rat is estimated to be about 1/5 of the degree of reorganization between humans and the rodent species.
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