Security considerations in blinded exposure experiments using electromagnetic waves

Whether exposure to electromagnetic fields well below accepted exposure limits has a cytogenetic effect on human cells has long been debated. It is widely published and generally accepted that the exposure unit invariably used in these experiments is capable of providing blinded exposure conditions. The following short report illustrates, however, that exposure conditions might not always be as effectively masked as is generally assumed.     

小麦-华山新麦草抗全蚀病新种质的分子细胞遗传学研究

对小麦-华山新麦草附加系H20和代换系H1的抗病性及分子细胞遗传学进行了研究。结果 表明,H20和H1的体细胞染色体数目范围分别为42～44和40～42,2n=44和2n=42的细胞频率分别为58.33%和90%;花粉母细胞减数分裂中期Ⅰ,染色体构型分别为21．55Ⅱ十0．90Ⅰ和20．74Ⅱ十0．52Ⅰ,22Ⅱ和21Ⅱ的细胞频率分别为61．56％和86．18％;与中国春测交,21Ⅱ十1Ⅰ和20Ⅱ十2Ⅰ的细胞频率分别为70．14％和88．59％。用华山新麦草基因组DNA作探针进行原位杂交,结果显示H20和H1中均有2条华山新麦草染色体,他们的染色体构成分别为2n=44=42W 2N和2n=42=40W 2N。对全蚀病菌,H20表现近高度抗病性,H1表现中度抗病性。     

Ogura CMS紫菜苔×萝卜×甘蓝型油菜杂种的获得及细胞遗传学研究

以OguraCMS紫菜苔×萝卜杂种F1(AR ,2n =19)为母本 ,以甘蓝型油菜 (AACC ,2n =38)为父本进行杂交 ,获得了 4棵杂种植株。其中 1株 (PRN 1)的花色为嵌合体 ,该植株上的花多为黄色 ,但是也有乳白色花 ,另外还有 1朵花甚至 1个花瓣上同时具有黄色和白色区域 ,其余 3株 (PRN 2、 3、 4 )都开白花。PRN 4的花药开花前退化 ,其余 3株都可以看到 3～ 6枚花药 ,能够产生部分花粉 ,但是PRN 2的花粉不能被I2 KI溶液染色。PRN 2具有 4个蜜腺 ,PRN 1和PRN 3具有 2个蜜腺 ,PRN 4无可见蜜腺。在低温下PRN 2叶色正常 ,其余 3株幼叶表现不同程度缺绿。PRN 1的染色体数目为 2n =38,染色体平均配对构型为 14 6 7Ⅰ +10 0 7Ⅱ +1 0 6Ⅲ ,其染色体组构成可能是AACR ;PRN 2的染色体数目为 2n =35 ,染色体平均配对构型为 13 89Ⅰ +8 33Ⅱ +1 33Ⅲ +0 11Ⅳ ,PRN 3的染色体数目为2n =33,染色体平均配对构型为 14 0 0Ⅰ +7 82Ⅱ +1 0 0Ⅲ +0 0 9Ⅳ。PRN 4的染色体数目未能确定。与甘蓝型油菜回交后PRN 1～ 3植株各自产生了一定数量的种子 ,而PRN 4则未产生种子。对这些杂种及其后代的遗传及育种意义进行了讨论     

First chromosome number determinations in south-eastern South American species of Lupinus L. (Leguminosae)

Chromosome numbers are presented for the first time for 30 accessions of nine south-eastern South American Lupinus species. Chromosome numbers of 2 n = 32 and 34 were found for L. bracteolaris (three out of five accessions with 2 n = 32) and L. linearis (two out of three accessions with 2 n = 32), and of 2 n = 36 for L. gibertianus , L. lanatus, L. magnistipulatus , L. multiflorus , L. rubriflorus , L. reitzii and L. uleanus . All the South American species examined have relatively low chromosome numbers when compared with most of the Old World and North American species. Our results, where 2 n = 36 is the rule, are in sharp contrast to the data for North American Lupinus species and reveal the following: (1) low chromosome numbers are the rule, at least in the southern part of eastern South America; (2) cytologically, the eastern South American species form a group distinct from the North American taxa; (3) high levels of polyploidy have not played as important a role in evolution and speciation in eastern South America as in North America; (4) the predominance of low chromosome numbers in eastern South American species and the existence of similar numbers in two of the six rough-seeded Old World species support the hypothesis that in the evolution of the genus the eastern South American species branched off first, followed by the rough-seeded group.  © 2002 The Linnean Society of London, Botanical Journal of the Linnean Socety , 2002, 139 , 395–400.     

Cranial and chromosomal geographic variation in manatees (Mammalia: Sirenia: Trichechidae) with the description of the Antillean manatee karyotype in Brazil

We employed landmark‐based 3D geometric morphometrics to assess cranial size and shape diversification in Trichechus manatus and T. inunguis to compare it with patterns among all manatee taxa (T. manatus latirostris, T. m. manatus, T. inunguis and T. senegalensis), and to analyse geographic variation within American manatee populations, using a sample of 189 skulls. Chromosome G‐ and C‐banding techniques were performed in T. m. manatus from Brazil. All taxa were statistically discriminated by skull shape. Trichechus m. manatus and T. m. latirostris have larger skulls than T. inunguis. A morphological discontinuity was noted within T. m. manatus, with the Brazilian population south of the Amazon discriminated from the T. m. manatus Caribbean and T. m. latirostris USA populations. Specimens from Suriname and Guyana had a skull shape more similar to the one from the Caribbean population. The Brazil Antillean manatee population exhibited morphological differences similar in magnitude to those found between the Amazonian and African species. Additionally, structural chromosome differences were detected between that population (chromosome pair 4 is metacentric and 10 is submetacentric) and manatees from Puerto Rico and Florida. Based on such morphological discontinuity and chromosomal divergence, we hypothesize that the Amazon River mouth may be acting as a reproductive barrier for the T. m. manatus population in Brazil, thus indicating that its taxonomic status and conservation strategies need an urgent reassessment.     

The politics of biomedical platforms: controversy around the molecularization of cytogenetics in prenatal diagnosis

The introduction of a new technique based on molecular cytogenetics (the comparative genomic hybridization microarray, Chromosomal Micro-Array) in prenatal diagnosis is here used as an occasion to politically elaborate Cambrosio’s and Keating’s framework of “biomedical platform.” The uncertainty generated by molecularization leaves the field open for two different modalities of implementation: using targeted microarrays to completely replace traditional karyotyping versus using genome-wide analysis of chromosomal anomalies only in at-risk pregnancies. Retracing the global scientific controversy on this issue and, particularly, the heated debate that has taken place in Italy, the paper intends to analyze the rise of a biomedical platform in prenatal diagnosis as a multi-layered phenomenon. Diverging epistemological strategies to deal with uncertainty, professional interests, relationship between medical practice, innovation and research, and patient subjectivities interact with each other, by shedding light on the inherent political dimension in the epistemological and material of an emerging biomedical platform.     

家蚕细胞遗传学及其应用

由于家蚕染色体数目较多、着丝粒弥散, 在较长时期内, 家蚕染色体识别、核型分析、染色体结构和功能的研究都受到很大限制。近年来, 应用比较基因组杂交、基因组原位杂交、基于细菌人工染色体克隆的原位杂交技术建立了家蚕的细胞学图, 综合分子连锁图构建高密度的细胞遗传学图已成为可能。分子细胞遗传学的应用正在推动家蚕染色体结构和功能的研究, 揭示出家蚕W染色体密集地分布着嵌套结构的逆转座子, 染色体端粒由重复序列(TTAGG)n以及端粒特异的非长末端逆转座子TRAS1和SART1组成, TRAS1、SART1具有较高的转录活性, 可能与维持染色体的稳定性有关。     

Long-term genome diploidization in allopolyploid Nicotiana section Repandae (Solanaceae)

Here, we analyze long-term evolution in Nicotiana allopolyploid section Repandae (the closest living diploids are N. sylvestris, the maternal parent, and N. obtusifolia, the paternal parent). We compare data with other more recently formed Nicotiana allopolyploids. We investigated 35S and 5S nuclear ribosomal DNA (rDNA) chromosomal location and unit divergence. A molecular clock was applied to the Nicotiana phylogenetic tree to determine allopolyploid ages. N. tabacum and species of Repandae were c. 0.2 and 4.5 Myr old, respectively. In all Repandae species, the numbers of both 35S and 5S rDNA loci were less than the sum of those of the diploid progenitors. Trees based on 5S rDNA spacer sequences indicated units of only the paternal parent. In recent Nicotiana allopolyploids, the numbers of rDNA loci equal the sum of those of their progenitors. In the Repandae genomes, diploidization is associated with locus loss. Sequence analysis indicates that 35S and 5S units most closely resemble maternal and paternal progenitors, respectively. In Nicotiana, 4.5 Myr of allopolyploid evolution renders genomic in situ hybridization (GISH) unsuitable for the complete resolution of parental genomes.     

Chromosomal evidence of incipient speciation in the Afrotropical malaria mosquito Anopheles funestus

The analysis of chromosomal polymorphism of paracentric inversions in anopheline mosquitoes has often been instrumental to the discovery of sibling species complexes and intraspecific genetic heterogeneities associated with incipient speciation processes. To investigate the population structure of Anopheles funestus Giles (Diptera: Culicidae), one of the three most important vectors of human malaria in sub-Saharan Africa, a three-year survey of chromosomal polymorphism was carried out on 4,638 karyotyped females collected indoors and outdoors from two villages of central Burkina Faso. Large and temporally stable departures from Hardy-Weinberg equilibrium due to significant deficits of heterokaryotypes were found irrespective of the place of capture, and of the spatial and temporal units chosen for the analysis. Significant linkage disequilibrium was observed among inversion systems on independently assorting chromosomal arms, indicating the existence of assortative mating phenomena. Results were consistent with the existence of two chromosomal forms characterized by contrasting degrees of inversion polymorphism maintained by limitations to gene flow. This hypothesis was supported by the reestablishment of Hardy-Weinberg and linkage equilibria when individual specimens were assigned to each chromosomal form according to two different algorithms. This pattern of chromosomal variability is suggestive of an incipient speciation process in An. funestus populations from Burkina Faso.     

A comparison of five hybrid zones of the weta Hemideina thoracica (Orthoptera: Anostostomatidae): degree of cytogenetic differentiation fails to predict zone width

Abstract Tension zones are maintained by the interaction between selection against hybrids and dispersal of individuals. Investigating multiple hybrid zones within a single species provides the opportunity to examine differences in zone structure on a background of differences in extrinsic factors (e.g., age of the zone, ecology) or intrinsic factors (e.g., chromosomes). The New Zealand tree weta Hemideina thoracica comprises at least eight distinct chromosomal races with diploid numbers ranging from 2n = 11 (XO) to 2n = 23 (XO). Five independent hybrid zones were located that involve races differing from one another by a variety of chromosomal rearrangements. The predicted negative correlation between extent of karyotypic differentiation (measured in terms of both percent of genome and number of rearrangements) and zone width was not found. Conversely, the widest zones were those characterized by two chromosome rearrangements involving up to 35% of the genome. The narrowest zone occurred where the two races differ by a single chromosome rearrangement involving approximately 2% of the genome. The five estimates of chromosomal cline width ranged from 0.5 km to 47 km. A comparative investigation of cline width for both chromosomal and mitochondrial markers revealed a complex pattern of zone characteristics. Three of the five zones in this study showed cline concordance for the nuclear and cytoplasmic markers, and at two of the zones the clines were also coincident. Zones with the widest chromosomal clines had the widest mitochondrial DNA clines. It appears that, even within a single species, the extent of karyotypic differentiation between pairs of races is not a good predictor of the level of disadvantage suffered by hybrids.