Somatic chromosomes of 307 seedlings of Pseudotsuga menziesii (Mirb.) Franco var. menziesii from four native localities in Canada and 203 seedlings of P. menziesii var. glauca (Beissn) Franco from two localities in U.S.A. were stained with guanine-specific chromomycin A3 (CMA). The chromosome complements (2n=26) of the two varieties were commonly composed of ten metacentric, 12 submetacentric and four telocentric chromosomes. Six thick CMA-bands appeared in the interstitial region of a pair of metacentric chromosomes and in the proximal regions of the long arms of two pairs of submetacentric chromosomes. However, the CMA-bands varied in size among the members of the populations. The large CMA-bands of the submetacentric chromosome were observed more frequently in var. glauca than in var. menziesii. Frequency of each sized CMA-band varied within the populations or the varieties. Bright CMA-blocks were associated to nucleoli in the interphase nucleus and the CMA-bands were coincided in location with the secondary constrictions. Ribosomal DNA hybridized in situ to the thick CMA-band regions.
Detailed localization of NORs on metaphase chromosomes of the Australian ant Myrmecia croslandi were examined using rDNA: DNA in situ hybridization. In individuals with 2K=1M(1+2)+1SM 1+1M2 (2n=3) NORs are located at the proximal region of the short arm heterochromatin block in 1M(1+2), and at the chromosomal gap in the heterochromatic short arm of M2. These findings were supported by cytological evidence that nucleoli appeared exactly at the expected NOR sites. There was no silver staining at any of the metaphase NORs in this ant, but rather the kinetochores stained faintly.
The genetic variabilities of sternopleural and abdominal bristle numbers existing in local natural populations were assessed. Using second chromosome lines of Drosophila melanogaster extracted from three natural populations in Japan (the Ishigakijima, Ogasawara and Aomori populations), experiments were conducted to estimate the components of genetic variances, additive and dominance variances. The following results were obtained: For both sternopleural and abdominal bristle numbers, the additive genetic variances (σ2A) were much larger than the dominance variances (σ2D) especially in the southern populations. For example, in the Ishigakijima population, for females sternopleural bristle numbers of the inversion-free chromosome group, the additive and dominance variances were estimated to be 1.2554 ± 0.2034 and 0.0552 ± 0.0180, respectively. The magnitudes of the estimates of additive genetic variances were nearly equal from north to south. By comparing the additive genetic variances of the inversion-free chromosome group with those of the In(2L)t-carrying chromosome group, it was inferred that sufficient number of generations to achieve the equilibrium state has not passed since the introduction of a single or a small number of the In(2L)t-carrymg chromosomes to the Ishigakijima population.
A quantitative genetic analysis was conducted on emigration response behavior using 140 second chromosome lines of Drosophila melanogaster. Fourteen sets of 5 × 5 partial diallel cross experiments were made in the parental generation. The emigration activity per batch of 50 male and 50 female F1 progeny was scored with Sakai's population system. Sexual difference did not appear in the emigration activity in these experiments. A significant genotype × sex × set interaction was detected. The genetic variance components of emigration activity differed between sexes: In males, additive genetic variance of emigration activity was 0.0497 ± 0.0092 and dominance variance, 0.0018 ± 0.0046; in females, additive, 0.0373 ± 0.0076 and dominance, 0.0169 ± 0.0044. Additive genetic correlation between sexes for the emigration activity was 0.685 ± 0.150, deviating significantly from unity. These results suggested that the genes affecting emigration activity would operate differently between sexes of D. melanogaster in natural populations.
An extremely early line of rice, T65·ER-20, was bred after 8 times of backcrossings, using two early heading lines, Kokusyokuto-2 harboring several unknown earliness genes besides the earliness gene Ef-1 as a donor parent of earliness genes, and an isogenic line of Taichung 65 (T65) harboring the Ef-1 gene (T65·ER-1) as a recurrent parent. Since extremely early and early individuals segregated in a 3:1 ratio in the B8F2 generation and in a 1:1 ratio in the B9F1, T65·ER-20 harbors a new dominant earliness gene, Ef-x, besides the Ef-1 gene. T65·ER-21 having the new earliness gene was also bred. Segregation mode for heading time in F2 plants showing disgenic segregation for two earliness genes, Ef-1 and Ef-x, was different between experiments conducted in the natural field and in the green house field. Extremely early, early and late individuals segregated in a 9:3:4 ratio in the former and in a 9:6:1 ratio in the latter. Then, the Ef-x gene was asserted to show an allele specific interaction to genes on the Ef-1 locus, and an action for earliness by itself was accelerated in the high temperature condition. A screening test surveying a chromosome carrying the Ef-x gene by the use of 40 RT-lines implied that it located on the second chromosome.
Heat denaturation experiments revealed heat stability differences at a locus encoding glucosephosphate isomerase (GPI) in the guppy. Inheritance experiments indicated that the observed differences in heat stability are controlled by a single incomplete dominant autosomal locus.
The sequence of a novel cDNA clone, Aiv-1, for tomato acid invertase was similar to that of TIV1 (Klann et al, 1992) for the enzyme except for a unique intron-like insertion. It is considered that Aiv-1 is derived from either an alternatively spliced mRNA for an isozyme or a pre-mRNA of TIV1.