Simple sequences

Simple sequences (or microsatellites) are stretches of monotonous repetitions of short (1–5 bp) nucleotide motifs that are distributed across the whole genome in eukaryotes. They are probably generated by slippage during replication and their primary mutation rate seems to be controlled predominantly by the efficiency of the mismatch repair system. Although most mutations in simple sequence loci appear to be neutral, some mutations in particular stretches have been implicated as having a role in human genetic diseases.     

Paternity assessment and population subdivision in a natural population of the larger mouse-eared bat Myotis myotis

A hypervariable simple sequence locus and mitochondrial D-loop sequences were used to analyse genetically a natural population of the larger mouse-eared bat Myotis myotis in southern Bavaria. Tests for population subdivision and direct observations suggest that females return to their natal sites, while males disperse. The males present in female nursery colonies are not related to the females. Paternity assessment for 46 offspring from a particular nursery colony showed that there are no males that monopolize the reproduction, and that the resident males in the colony had only a small mating success. Instead, the results suggest that females actively seek matings outside their colony. Most interestingly, it appears that a group of males about 16 km away from the nursery colony had a relatively high mating success and that this group of males may be related to the females of the nursery colonies. If this finding can be confirmed in a larger study, it may have important consequences for future conservation strategies.     

Stimulus coding in crayfish antennal mechanoreceptors estimated by noise analysis

Two different kinds of mechanoreceptive hairs (smooth and feathered) on the second antennae of the freshwater crayfish, Orconectes virilis, have been investigated for their stimulus coding propertics. These mechanoreceptors show a great deal of non-linear behaviour both in threshold and in directionality. An effective appraoch for the investigation of such systems is noise analysis in the frequency domain. This method has been used here to calculate zero-, first- and second-order kernels. Sensory cells reveal different first- and second-order kernels, depending on which type of hair is being stimulated. The first-order kernel has a pronounced peak in the frequency response at 110 Hz if a feathered hair is stimulated and at 60 Hz if a smooth hair is stimulated. The second-order kernel shows a number of pronounced peaks in the frequency response between 40 and 110 Hz, but only if a feathered hair is stimulated. Smooth hair stimulation results in less sharp peaks but in higher gain for the same range of stimulus frequencies.     

Sequence of a novel HLA-DQB1 allele

The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence data base and have been assigned the accesion number M74842. The name DQB1*0304 has been officially assigned by the WHO Nomenclature Committee in November 1991. This follows the agreed policy that, subject to the conditions stated in the most recent Nomenclature Report (WHO Nomenclature Committee for factors of the HLA system, 1991), names will be assigned to new sequences as they are identified. List of such new names will be published in the following WHO Nomenclature Report.     

Asynchronous mitotic domains during blastoderm formation inMusca domestica L. (Diptera)

Summary We describe the mitotic cleavage patterns during blastoderm stage of the house flyMusca domestica L. Nuclear divisions up to mitotic stage 11 are apparently synchronous. Beginning with stage 12, nuclear divisions in the posterior third of the embryo lag behind, resulting first in a parasynchronous and finally in an asynchronous cleavage pattern. Thus a stage exists where all nuclei in the anterior region have completed 14 nuclear division cycles, while those in the posterior region have completed only 13 cycles. The border region between these nuclei is well defined and lies at 35% EL (egg length), the expression border of a gap gene. This border region is about 4–5 nuclei wide and shows a specialized mitotic behaviour.