The behaviour of B-chromosomes in meiosis was studied in 44 males of yellow- necked mouse, Apodemus flavicollis. The Bs behave in a non-Mendelian fashion during meiosis I i.e., appear as univalents, regardless of the number of Bs, and segregate in a random fashion. The meiotic drag of Bs, resulting from Bs lagging and premature division of Bs into chromatids, was found in 1B animals. The Bs drag amounts to about 6% of cells and is not substantial; however due to dispensable nature of Bs, it has to be compensated through drive in females or heterotic effects of Bs. This result gives support for the heterotic model of Bs evolution in A. flavicollis. On the other hand, the number of chiasmata on A-chromosomes showed increasing tendency with the number of Bs in the karyotype. As the chiasma effect is characteristic for parasitic Bs, it gives support for the parasitic model of Bs evolution. With contrasting results, the hypothesis of a combined model of Bs evolution, in which the fitness of B-bearers changes around the year or in different environmental conditions is discussed.
A method for B-spline filtration of data measured on a very precisely manufactured sphere is described in this paper. The method has been developed to decrease the uncertainty of measurement which can be obtained by least squares method commonly used when processing the measured data. The B-spline filtration is realised as a B-spline surface approximating the data measured on 3D coordinate measuring machine and transformed into the parametric space of the sphere. This transformaton eliminates the undesirable consequences of convex hull property of B-spline surfaces when processing convex data. Furthermore, the B-spline representation of the measured sphere can be considered as a certain replacement of the original sphere. Subsequently, the B-spline representation can be used for a new more precise measuring strategy in iterative measuring process. and Obsahuje seznam literatury