The amount of chlorophyll-deficient and morphological abnormality genes concealed in natural populations of wild radish, Raphanus sativus var. hortensis f. raphanistroides, was estimated by conducting self-fertilization by means of bud pollination. The frequencies of three mutant genes, green hypocotyl(g), green silique(gs) and hairy silique(hy), were also estimated from the frequency of the self-pollinated lines that segregated mutant homozygotes in the S1 progeny. The frequency of chlorophyll-deficient mutant alleles is within the range expected from the mutation-selection balance theory of population genetics. However, the frequencies of g, gs and hy are higher, on the average 20.5%, 3.6% and 10.6%, respectively, than the frequencies expected from mutation-selection balance. The frequencies did not show any systematic geographical change, nor are they correlated to any particular environmental factors. Hence, the mechanisms that maintain these mutant alleles remain unknown.
We used allozyme loci, join-count statistics, and Moran's spatial autocorrelation statistics to quantify the spatial genetic structure caused by clonal reproduction from that maintained in sexually reproduced individuals in a population of distylous shrub Abeliophyllum distichum, a monotypic genus endemic to the central Korea. The population harbors high levels of multilocus genotypic diversity (mean DG = 0.960). Join-count statistics showed that there were statistically significant clustering of clonal genotypes within distances < 6 m. Both the entire population and the set of sexually reproduced individuals exhibited significant spatial autocorrelation up to the scale of about < 10 m, and the sexually reproduced individuals are in a substantially structured, isolation by distance, manner. This indicated that gene flow would not be extensive in a population of A. distichum because of pine forest acting as a shield for wind movement. Probable unequal ratio of the two floral morphos, selfing via matings between clones, and/or consanguineous matings may be factors for decreasing seed sets observed in the populations of the species ("inbreeding depression"). It is recommended that the sampling for conservation purposes might be performed at a diameter of more than 13 m to extract the genetic diversity across an entire population.
Muscarinic acetylcholine receptors in mammals consist of five subtypes (M1-M5) encoded by distinct genes. They are widely expressed throughout the body and play a variety of roles in the peripheral and central nervous systems. Although their pharmacological properties have been studied extensively in vitro, colocalization of the multiple subtypes in each tissue and lack of subtype-specific ligands have hampered characterization of the respective subtypes in vivo. We have mapped mouse genomic loci for all five genes (Chrm1-5) by restriction fragment length variant (RFLV) analyses in interspecific backcross mice. Chrm1, Chrm2, and Chrm3 were mapped to chromosome (Chr) 19, 6, and 13, respectively. Both Chrm4 and Chrm5 were mapped to Chr 2. Although a comparison of their map positions with other mutations in their vicinities suggested a possibility that the El2 (epilepsy 2) allele might be a mutation in Chrm5, sequencing analyses of the Chrm5 gene in the El2 mutant mice did not support such a hypothesis.
Restriction fragment length polymorphism (RFLP) of mitochondrial DNA in the genus Oryza was surveyed using 20 accessions including 11 species and a single endonuclease, EcoRI. RFLPs were visualized by Southern hybridization with eight rice mitochondrial DNA probes labeled non-radioactively with digoxigenin-dUTP. A total of 66 bands were obtained from all of the accessions. The total number of fragments per plant was higher in diploid A-genome species (an average of 35.3) than that in diploid B- and C-genome species and allotetraploid BC- and CD-genome species (an average of 28.2). The extent of the polymorphism in the RFLP patterns was various depending on the probes used. A diverse polymorphism was observed with most of the probes used, i.e. the cob, cox I, atp6, rrn18, rrn26 and atp9 regions, whereas, no polymorphic band was observed with a probe for the coxII region. The genus Oryza was separated into two large clusters. One cluster was comprised of A-genome species and the other cluster was comprised of B-, BC-, C-, and CD- genome species. Within A-genome species, the genetic variation was relatively high. Even in O. sativa species, the RFLP patterns of japonica and indica subspecies were clearly different from each other when three probes were used. However, there was no polymorphism between O. glaberrima and O. barthii. Within the genomes of B, BC, C, and CD, RFLP patterns were similar to each other and they showed a closer affinity except for O. minuta (BBCC). Within the BC genome species, the patterns of O. punctata and O. minuta were largely different from each other and separated into two different subclusters. Thus, the mitochondrial genomes of the two BC species (O. punctata and O. minuta) apparently evolved independently. Among CD genome species (O. latifolia and O. alta), the patterns of one accession, O. alta W0017 were largely different from those of the other accessions of CD genome species.
In conjugation of Tetrahymena thermophila, the paroral zone, cortical cytoplasm in the vicinity of the cytostome, is the site where nuclear selection occurs; one of the four meiotic products is selected in this site prior to the production of gametic pronuclei. During inbreeding cross experiments, several sterile strains were obtained which showed aberrant nuclear behavior. Conjugants of these strains normally underwent meiosis, resulting in the generation of four meiotic products. They, however, failed to complete the process of nuclear selection and aborted the subsequent conjugation sequences. During nuclear selection, macronucleus was frequently selected instead of a meiotic product. A novel aberrant nuclear behavior was observed: Macronucleus and a meiotic product were jointly selected and the both nuclei simultaneously attached to the same paroral zone. When this simultaneous attachment occurred in one partner cell of a pair, nuclear selection was never observed in the other partner cell. This result suggests that a conjugating pair has only two attachment sites on the paroral zone during nuclear selection, and that the distribution of the sites is occasionally distorted in abortive conjugation.