IRENE newsletter. Volume 6, number 2 (Fall/Winter 2012)

IRENE’s mission is to improve the health and well-being of Iowans through collaboration in practice-based research on questions important to primary care physicians and their patients. IRENE’s purpose is to create and foster a network of research collaboration between the academic medical center and primary care physicians through out the state of Iowa with a particular focus on improving rural health.

Linear relations between writhe and minimal crossing number in Conway families of ideal knots and links

We showed earlier how to predict the writhe of any rational knot or link in its ideal geometric configuration, or equivalently the average of the 3D writhe over statistical ensembles of random configurations of a given knot or link (Cerf and Stasiak 2000 Proc. Natl Acad. Sci. USA 97 3795). There is no general relation between the minimal crossing number of a knot and the writhe of its ideal geometric configuration. However, within individual families of knots linear relations between minimal crossing number and writhe were observed (Katritch et al 1996 Nature 384 142). Here we present a method that allows us to express the writhe as a linear function of the minimal crossing number within Conway families of knots and links in their ideal configuration. The slope of the lines and the shift between any two lines with the same

Restricted gene flow at specific parts of the shrew genome in chromosomal hybrid zones.

The species and races of the shrews of the Sorex araneus group exhibit a broad range of chromosomal polymorphisms. European taxa of this group are parapatric and form contact or hybrid zones that span an extraordinary variety of situations, ranging from absolute genetic isolation to almost free gene flow. This variety seems to depend for a large part on the chromosome composition of populations, which are primarily differentiated by various Robertsonian fusions of a subset of acrocentric chromosomes. Previous studies suggested that chromosomal rearrangements play a causative role in the speciation process. In such models, gene flow should be more restricted for markers on chromosomes involved in rearrangements than on chromosomes common in both parent species. In the present study, we address the possibility of such differential gene flow in the context of two genetically very similar but karyotypically different hybrid zones between species of the S. araneus group using microsatellite loci mapped to the chromosome arm level. Interspecific genetic structure across rearranged chromosomes was in general larger than across common chromosomes. However, the difference between the two classes of chromosomes was only significant in the hybrid zone where the complexity of hybrids is expected to be larger. These differences did not distinguish populations within species. Therefore, the rearranged chromosomes appear to affect the reproductive barrier between karyotypic species, although the strength of this effect depends on the complexity of the hybrids produced.

PathBeat. Number 1 (May 2000) University of Iowa Department of Pathology.

University of Iowa Department of Pathology newsletter.

PathBeat. Number 2 (October 2000) University of Iowa Department of Pathology.

University of Iowa Department of Pathology newsletter.

PathBeat. Number 3 (December 2001) University of Iowa Department of Pathology.

University of Iowa Department of Pathology newsletter.

PathBeat. Number 4 (December 2002) University of Iowa Department of Pathology.

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PathBeat. Number 5 (July 2003) University of Iowa Department of Pathology.

University of Iowa Department of Pathology newsletter.

PathBeat. Number 6 (July 2004) University of Iowa Department of Pathology.

University of Iowa Department of Pathology newsletter.

PathBeat. Number 7 (May 2005) University of Iowa Department of Pathology.

University of Iowa Department of Pathology newsletter.

PathBeat. Number 8 (Summer 2008) University of Iowa Department of Pathology.

University of Iowa Department of Pathology newsletter.

PathBeat. Number 9 (Winter 2008) University of Iowa Department of Pathology.

University of Iowa Department of Pathology newsletter.

PathBeat. Number 10 (Summer 2009) University of Iowa Department of Pathology.

University of Iowa Department of Pathology newsletter.

PathBeat. Number 11 (Spring 2010) University of Iowa Department of Pathology.

University of Iowa Department of Pathology newsletter.

PathBeat. Number 12 (Spring 2011) University of Iowa Department of Pathology.

University of Iowa Department of Pathology newsletter.