Showing papers in "Hereditas in 2008"

The Allium test as a standard in environmental monitoring

Abstract: The Allium test is suggested as a standard in environmental monitoring, e. g. as a part of a test battery. Background, the method including suggested parameters for standard use, results from various application areas and comparisons with a number of other test systems are presented. The Allium test is a short-term test with many advantages: low cost, ease to handle, good chromosome conditions for the study of chromosome damage or disturbance of cell division including the evaluation of risks of aneuploidy. The ability of the root cells to activate promutagens (the MFO-system) further widens the application areas of the Allium test. The use of series of onions for each concentration of the test chemical allows statistical considerations, and from growth curves Effect-Concentration values are obtained. The Allium test is, lastly, a sensitive test showing good correlation to other test systems. Thus, positive results in the Allium test should be considered as a warning and also an indication that the tested chemical may be a risk to human health and to our environment.

Standard karyotype of the domestic pig. Committee for the Standardized Karyotype of the Domestic Pig.

Abstract: Identification des bandes chromosomiques du porc en regions cytologiquement definies utilisables pour les descriptions de caryotypes normaux et aberrants

Genetic instability in the human population: A working hypothesis1,2

Abstract: In several rare syndromes, genetic instability, expressed as chromosome instability, is known. Patients with these syndromes are predisposed to cancer. Evidence has been accumulating to show that chromosome instability occurs in some other diseases also, though the frequency was not as high. Genetic instability may induce mutational events in a chromosome (second step) whose homolog has a congenital defect (primary step) towards neoplasia in a target cell. Genetic instability may also induce the initial step. It is highly probable that genetic instability in the human population is not an all-or-none situation. Gradations of genetic instability may exist with a variety of underlying causes. Persons may have latent instability which normally cannot be detected by cytogenetic methods, e.g. defective DNA repair mechanisms. With DNA damage, there will be little or no repair in the cells of persons with defective repair systems, hence more chromosomal aberrations. When challenged with clastogens, the cells of persons with mildly defective repair systems may show a higher rate of chromosome aberrations than those of stable persons. This paper presents a working hypothesis on genetic instability in the human population and methods to detect the masked instability.

Interspecific hybridization with cultivated barley (Hordeum vulgare L.)

Abstract: Hordeum vulgare was intercrossed with 26 wild Hordeum species representing 37 cytotypes. Seed set was obtained from all crosses, whereas adult plants (hybrids or haploids) resulted from only 22 of the intercytotype combinations (15 species). Crosses were more successful when Hordeum vulgare was used as the pollen donor rather than as the female parent. Combinations with diploid cytotypes were difficult to obtain. In spite of good seed set, flowering diploid combinations were obtained in only three combinations, viz. with H. marinum, H. depressum, and H. brachyantherum. Haploids resulting from chromosome elimination were established in four combinations, viz. with H. marinum, 2x and 4x, H. brachyantherum, 6x, and with H. leehleri, 6x (the last mentioned giving hybrids as well as haploids). Generally, variation in somatic and meiotic chromosome numbers was observed in the hybrids. Meiotic pairing, studied in 13 combinations, was low except in the hybrid with H. hulbosum. Some indications of a genetic regulation of the meiotic pairing were found.

Patterns of the early, gross chromosomal changes in malignant human gliomas

Abstract: Chromosomal findings by banding in 12 malignant human gliomas demonstrated clearly that simple numerical changes are the primary gross deviations in gliomas. So far, these numerical primary deviations fall into three different groups: (1) gliomas showing a loss of a gonosome, (2) tumors with gains of No. 7 (and at the same time often also losses of No. 10), and (3) cases with losses of No. 22. The further evolution seems to be characterized by a variety of partly nonrandom numerical and also structural changes. The aberration of double-minutes (DMs), found in half of our cases, might be such a non-random anomaly. If (as suggested by recent reports in the literature) the DMs correlate with activation of an amplified oncogene, then this anomaly might indicate a special subsequent step in oncogenesis or it might even in some cases represent an alternative to the seemingly primary numerical deviations and precede them.

Hierarchical gene diversity analysis and its application to brown trout population data

Abstract: A generalized FORTRAN IV computer program (NEGST) for nested gene diversity analysis and its application to brown trout gene frequency data are presented. In its present shape the program handles up to five hierarchical levels of subdivision, 70 operational units (subpopulations), and 50 polymorphic loci with 20 alleles per locus.

Effect of inbreeding on genetic relatedness

Abstract: The effect of inbreeding on genetic relatedness (intragroup genotypic correlation) is examined in several models with special emphasis on social Hymenoptera (all male-haploid) living in nests. Inbreeding takes place in the form of intranidal matings, and the models are developed for polygyny (several females reproducing in one nest) and polyandry. The latter models are also developed for diploid populations. The equations derived here are applied to the population data from the ant Formica exsecta.

Relationships in the barley genus (Hordeum): an electrophoretic examination of proteins

Abstract: The relationships between all known Hordeum species except H. guatemalense were inferred from the electrophoresis of the six enzyme systems Got, 6-Pgd, Mdh, Idh, a-and B-amylases. A total of eleven loci were scored for in these systems. Maximum likelihood clusters and Wagner networks calculated from the electrophoretic data divided the genus into three groups, viz. the “H. vulgare group”, the “H. marinum group” and the “H. pubiflorum group”. Only one of these groups was recognized in the morphological sectioning of the genus. Most of the polyploid cytotypes in the genus seemed to have originated as alloploids. Phylogenetic links between diploid and polyploid taxa are suggested from the enzyme phenotypes. An evolutionary theory for the genus Hordeum is proposed, with two centres of differentiation, in South-West Asia and South America, respectively.

Effects of trivalent and hexavalent chromium on root growth and cell division of Allium cepa

Abstract: The effects of trivalent and hexavalent chromium on root growth, cell division and chromosome morphology of Allium cepa were studied. The concentrations used of chromium nitrate and potassium dichromate were 2 × 10-1, 2 × 10-2, 2 × 10-3, 2 × 10-4, 2 × 10-5, 2 × 10-6, and 2 × 10-7M. The results showed that both trivalent and hexavalent chromium inhibit root growth and cause mitotic irregularities comprising c-mitosis, anaphase bridges, chromosome stickiness, and chromosome fragmentation and lagging. When compared with chromium nitrate on the equimolar basis, potassium dichromate showed a stronger inhibitory and toxic effect on root growth and cell division, respectively. The possible mechanism of the Cr poisoning of root meristem cells of Allium cepa is also briefly discussed.

Patterns of phenotypic diversity in an Ethiopian barley collection, and the Arussi‐Bale Highland as a center of origin of barley

Abstract: 485 land race populations of barley collected from 91 Minimum Package areas spread over 12 provinces of Ethiopia were grown in the field and classified for number of kernel rows, spike length, awn type, spike density, rachilla hair, caryopsis, and kernel color. The different characters showed different levels of diversity by the Shannon-Weaver diversity index. Provinces were grouped into regions to detect possible differences in diversity within and among regions. Much of the variation in diversity is due to differences among characters; and no differences were detected among provinces and regions in the level of diversity, which could be due to insufficient sampling. A high diversity index (H'=0.72) was obtained for the Southwestern Plateau, and this was not significantly different from the value for Ethiopia (H'=0.68). Clinal patterns of variations were observed for some characters and localized concentrations for others. An attempt was made to explain these patterns based on climatic data and selection. Vavilov's theory of the emancipation of recessives was found to be untenable. A center of origin of barley is defined on the Arussi-Bale Highland in accordance with the requirements of the current concept of the center of origin; and the inadequacy of this concept is discussed. Disruptive selection is considered as the most probable cause of the maintenance of the diverse forms of barley in Ethiopia; and further detailed studies of the patterns of variation of barley in Ethiopia are recommended.

Chromosome aberrations and micronuclei in bone marrow cells and peripheral blood lymphocytes in humans exposed to ethylene oxide.

Abstract: Twenty-eight individuals occupationally exposed to ethylene oxide have been compared with 20 controls regarding cytogenetic effects in peripheral blood lymphocytes and in bone marrow cells The exposure levels of ethylene oxide were estimated and none of the individuals had, during the last 25 years, been exposed to workroom air concentrations exceeding 1 ppm The exposed persons showed significantly increased levels of chromosome aberrations in lymphocytes (about 50% increase of mean) and of micronuclei in erythroblasts and polychromatic erythrocytes (about 100% and 300% increase of mean, respectively) when compared with controls However, sister chromatid exchanges and micronuclei in lymphocytes did not show any significant effect of exposure A significant effect of smoking on micronuclei in erythroblasts and lymphocytes was found There were several statistically significant, positive correlation coefficients among the different cytogenetic parameters

Desirable characteristics in perennial Triticeae collected in China for wheat improvement

Abstract: Perennial Triticeae in China contain an enormous gene pool that has a great potential for wheat improvement. Collecting expeditions to 12 provinces of Northern China have been carried out. It has been found that most collections of Agropyron mongolicum, A. cristatum, A. desertorum, and Leymus chinensis, h. secalinus are drought tolerant, and that some collections of Hordeum brevisubulatum, Leymus chinensis are tolerant to saline-alkali soil. 448 accessions of perennial Triticeae were screened for resistance to powdery mildew, 248 accessions and 93 accessions were screened for resistance to BYDV strains PAV and RPV, respecitvely, and some species resistant to the diseases were found. A brief description of utilization of perennial Triticeae for wheat improvement in China is given in this paper.

Meiosis in interspecific Hordeum hybrids

Abstract: 36 hybrid families representing 29 interspecific and one intraspecific combinations between tetra- and hexa-ploid Hordeum species were analyzed for meiotic M I pairing. H. bulbosum, H. murinum, and H. marinum have quite separate genomes not related to the other species in the genus. H. bulbosum (with the I genome) and tetra- and hexaploid H. brevisubulatum (with the H genome) are autoploids. H. murinum (with the Y genome) and H. marinum (X genome) may also have had an autoploid origin, but have developed strong bivalent-forming genetic mechanisms. The pairing in the pentaploid hybrids including the five tetraploid species H. jubatum, H. brachyantherum, H. roshevitzii, H. tetraploidum, and H. fuegianum fitted throughout best with a 2:2:1 genomic model. They are segmental alloploids with the basic H genome together with a modification of it. The same modifications of the H genome are found in five hexaploid North and South American species. The pairing in hybrids including H. secalinum and H. capense fitted best with a 2:1:1:1 genomic model. Together with H. depressum they are alloploids with two unrelated genomes, one of which being the H genome. The other genome has not been detected among the hexaploid species. The interpretation of meiotic data in pentaploid hybrids is difficult, mainly because of the action of pairing-regulating genes and autosyndesis.

Electrophoretically detectable genetic variation in natural and hatchery stocks of Atlantic salmon in Finland.

Abstract: To survey the genetic resources of Atlantic salmon (Salmo salar L.) stocks in Finland, an electrophoretic study was made of natural and hatchery stocks. The stocks were compared with the nearest stocks in the USSR, and the effects of hatchery rearing were evaluated. The genetic variation within and between stocks was measured from 20 samples, of which three (Kola, Neva and Onega) were from the USSR. Twenty-five enzyme loci were examined, of which six were polymorphic: AAT-4, 1DH-3, ME-3, MDH-3, PGM-1, and SDH-1. The mean heterozygosity of all the populations was 4.2 % (1.0–7.2). For the natural salmon stocks of the Arctic Ocean, the mean heterozygosity was 6.3 %, for the natural stocks of Atlantic salmon in the Baltic 4.8 %, for the hatchery stocks 3.6 %, and for the lake salmon (Salmo salar m. sebago Girard) 1.8 %. The results are in agreement with the hypothesis that the amount of variation depends on the effective population size and that culture diminishes variation by decreasing the effective population size. All the stocks originating from different rivers differed from each other with statistical significance. The most unique stocks were the River Kola stock and the lake salmon stock from Lake Saimaa. The genetic distances were consistent with the geographic distance between the rivers from which the stocks originated. Stress is laid on the importance in fish culture of maintaining separate stocks and using larger brood stocks.

Isolation and cultivation of embryogenic microspores from barley (Hordeum vulgare L.).

Abstract: Two different techniques for mechanical isolation of microspores from the barley cultivar ‘lgri’ have been evaluated The anthers were subjected to mannitol pretreatment prior to microspore isolation, which was performed either by maceration with a pestle or by blending of the excised anthers The microspores were purified by centrifugation and washing and cultured in liquid medium on a membrane support In the following four weeks the microspores developed into embryoids, which were subsequently regenerated to plants on solid medium Microblending of the anthers was found to be more reproducible than pestle maceration, and the yield of large microspores was 100 % higher using this method With the microblending technique a mean of 94 green plants and 04 albino plants were regenerated per plated anther while a mean of only 28 green and 017 albino plants per anther were regenerated from microspores isolated after pestle maceration of the anthers Microspores isolated from mass cultures were also cultured as single cells in microdroplets, and it was shown that microspores isolated from 3-5 days old mass cultures could develop into plants although at a low frequency (03 X) Finally, the potential of using microinjection for transforming embryogenic microspores has been evaluated

Morphological diversity in tetraploid wheat landrace populations from the central highlands of Ethiopia

Abstract: Seven tetraploid wheat populations consisting of 122. entries collected from Shoa and Gojem Administrative Regions of Ethiopia. were studied for variation of eight morphological characters that have two or more phenotypic classes. Monomorphism was common in many of the populations for awn length and glume pubescence, whereas the rest of the Characters exhibited polymorphism in varying degrees. Awn condition was found to be a fixed character in the entire collection. The lowest level of diversity was observed for glume pubescence (excluding awn condition) and an intermediate to a high level of diversity for all the other characters There was no significant difference among all the estimates of mean diversity for the populations and districts. Although only glume pubescence showed significant differences, the analysis of variance of diversity for individual characters indicated most of the variation to be due to differences among districts rather than among populations within districts. This was also confirmed by a hierarchical analysis of variance of diversity, which detected significant difference only among districts. It is suggested that future collections should covet more different areas rather than having more samples from similar areas. The species composition of the collections is described. Possible adaptive mechanisms of some of the characters arc also discussed.

Molecular characterisation of indigenous Swedish apple cultivars based on SSR and S‐allele analysis

Abstract: Trees of 68 apple cultivars, aimed for preservation by the ‘National Program for diversity of cultivated plants’ as mandate cultivars, were analysed using a set of 10 SSR (simple sequence repeat) primer pairs and the self-incompatibility (S � )locus to evaluate genetic diversity and reveal inter-cultivar relationships. The 12 polymorphic SSR loci exhibited 2 to 15 alleles, with expected heterozygozity (He) ranging from 0.36 to 0.88 and a mean of 0.74. Numerous alleles were classified as rare or unique (35% and 18% respectively). For the S-locus, a total of 14 alleles were identified in this study. Five alleles, S1� S3 ,S 5 and S7 had frequencies ranging from 11 to 18%, whereas the remaining 9 alleles were below 6%. All sexually obtained cultivars could be distinguished with the set of SSR loci. Sports were identical with their progenitors in two cases, but differed in one SSR allele in a third case. An SSR-based dendrogram, based on Roger’s genetic distances, did not reveal any clear pattern of clustering. The genetic distances were, however, correlated with a corresponding matrix obtained in a previously conducted RAPD-based study of the same cultivars. Non-mandate parents of Swedish mandate cultivars together with some other reference cultivars were included in this study to check the accuracy of allele scoring, verify parentage and compare the results of this study with those presented in previously published studies. Some discrepancies in allele sizing were revealed and the possibilities of avoiding this problem are discussed.

QTL mapping for yield components in a tropical maize population using microsatellite markers

Abstract: QTL mapping provides usefull information for breeding programs since it allows the estimation of genomic locations and genetic effects of chromossomal regions related to the expression of quantitative traits. The objective of this study was to map QTL related to several agronomic important traits associated with grain yield: ear weight (EW), prolificacy (PROL), ear number (NE), ear length (EL) and diameter (ED), number of rows on the ear (NRE) and number of kernels per row on the ear (NKPR). Four hundred F2:3 tropical maize progenies were evaluated in five environments in Piracicaba, Sao Paulo, Brazil. The genetic map was previously estimated and had 117 microssatelite loci with average distance of 14 cM. Data was analysed using Composite Interval Mapping for each trait. Thirty six QTL were mapped and related to the expression of EW (2), PROL (3), NE (2), EL (5), ED (5), NRE (10), NKPR (5). Few QTL were mapped since there was high G×E interaction. Traits EW, PROL and EN showed high genetic correlation with grain yield and several QTL mapped to similar genomic regions, which could cause the observed correlation. However, further analysis using apropriate statistical models are required to separate linked versus pleiotropic QTL. Five QTL (named Ew1, Ne1, Ed3, Nre3 and Nre10) had high genetic effects, explaining from 10.8% (Nre3) to 16.9% (Nre10) of the phenotypic variance, and could be considered in further studies.

Chromosomal polymorphism and racial evolution of Sorex uruneus L. in Finland

Abstract: Halkka, L., Soderlund, V., Skaren, U. and Heikkila, J. 1987. Chromosomal polymorphism and racial evolution of Sorex araneus L. in Finland. —Hereditas 106: 257–275. Lund, Sweden. ISSN 0018–0661. Received October 2, 1986 Karyotypes of 197 Sorex araneus specimens from 26 populations throughout Finland were studied. Six chromosomal races with different combinations of arms, g, h, k, m, n, o, q and r were found to form chromosomes nos 3,5,7 and 8. The races may have evolved from a common ancestral karyotype through a series of reciprocal translocations. Postglacial geological development and distribution routes of Sorex support this hypothesis. Ancestor 3=qg, 5=nh, 7=rk, 8=om (Northern Russia)—race II 3=mg, 5=nh, 7=rk, 8=qo easternmost Finland) — race I 3=mg, 5=nh, 7=qk, 8=ro (Northern Finland and Lapland). Ancestor —race IV 3=qg, 5=nh, 7=ok, 8=rm (Central and Southern Finland, via Salpausselka ridge) — race V13, 5, 7, 8 =g, h, k, m, n, o, q, r (Aland Islands), race IV — race V3=k, g, 5=nh, 7=rm, 8=qo(Rauma, new centric fusion or hybrid). Ancestor — race III 3=qg, 5=kh, 7=om, 8=rn (Southeastern Finland, via Karlelian Isthmus). Chromosomes 3, 5, 7, 8, 4=li and 6=pi form an internal chromosomal polymorphism with two arms being combined to one metacentric chromosome (m) or being separated into two telocentric arms (t). The lowest frequencies of telocentrics were found in Central Finland and the highest, in Southwestern Finland and Aland. The chromosomal phenotypes mm, mt and tt seem to stay in Hardy-Weinberg equilibrium inside populations. The possible role of transposable elements in chromosomal evolution of Sorex araneus is discussed.

Multiple mating in Formica ants

Abstract: Mother-offspring analyses were carried out in three species of Formica ants in order to estimate the frequency of multiple mating and to test for randomness of mating. The mating types deduced on the basis of genotypic data agreed with the assumption of random mating in F. sanguine a and F. transkau-casica, whereas those in F. pressilabris departed from randomness. The results suggest that F. trans-kaucasica can be considered chiefly monoandrous. F. pressilabris shows a moderate frequency of double matings, and F. sanguinea females commonly mate with at least two males.

Relationships in the genus Hordeum: Giemsa C-banded karyotypes

Abstract: Giemsa C-banded karyotypes of the 32 Hordeum L. species incl. all subspecies and cytotypes divide them into four groups by chromosome banding patterns. Most taxa have a rather similar pattern with a number of more or less randomly disposed C-bands at centromeric, intercalary, and distal positions. This agrees with their grouping with a common genome, H. H. brevisubulatum s.l. is normally grouped with genome H, but the banding patterns of the five subspecies deviate by having a low number of centromeric and intercalary bands only (patterns vary from having no to very conspicuous C-bands at the telomeres). H. bulbosum has most C-bands at the centromeres, and H. vulgare, most C-bands at centromeric and juxtacentromeric positions. The overall resemblance of the C-banding patterns of H. bulbosum and H. vulgare supports that both carry the same genome, I. H. marinum and H. murinum each have a deviating karyotype. The corresponding genomes are preliminarily referred to as ‘X’ and ‘V’. In combination with chromosome number, and number and morphology of marker chromosomes, the C-banded karyotypes of a number of species are sufficiently distinct to be of use for identification and the study of relationships. Most Hordeum species of the Americas have similar C-banded karyotypes at the respective ploidy level, questioning the biological relevance of referring them to different sections.

Cytogenetical observations in five human anaplastic thyroid carcinomas

Abstract: Mark, J., Ekedahl, C., Dahlenfors, K. and Westermark B. 1987. Cytogenetical observations in five human anaplastic thyroid carcinomas. —Hereditas 107 163–174. Lund, Sweden. ISSN 0018–0661. Received January 14, 1987 Observations by banding methods in 5 human anaplastic thyroid carcinomas are reported. All tumors had a polyploid, often very flat, mode. Karyotype analyses, however, revealed that in spite of a mostly profound numerical-structural variability, all carcinomas were monoclonal products. Numerical deviations in common were proportional gains of No. 20 and often losses of Nos. 1,4and 13. Structural aberrations particularly common were a variety of Robertsonian translocations and isochromosomes. Double-minutes (Dms) were seen in 2 tumors. The Dms in one of these cases did not contain any of the oncogenes previously demonstrated to be amplified in human tumors harbouring correspondent aberrations. The present study indicates that undifferentiated thyroid carcinomas are easily established as cell lines. Because of this characteristic and, also, the suggestive common occurrence of Dms, the anaplastic carcinomas seem to comprise an unusually favourable material for future molecular studies.

Electrophoretic variation in large mammals. III. The ringed seal, Pusa hispida, the harp seal, Pagophilus groenlandicus, and the hooded seal, Cystophora cristata.

Abstract: Twenty-one enzymes and three proteins were resolved by starch gel electrophoresis from liver, muscle and blood samples of 102 Atlantic walruses (Odobenus rosmarus rosmarus (L.)) from the Thule district, North Greenland. Among 32 loci investigated, three were found to be polymorphic. Thus, the genetic variability in the Atlantic walrus is low as found in other large mammals, except man.

Analysis of regional patterns of phenotypic diversity in the Ethiopian tetraploid and hexaploid wheats

Abstract: Bekele, E. 1984. Analysis of regional patterns of phenotypic diversity in the Ethiopian tetraploid and hexaploid wheats. —Hereditas 100:131–154. Lund, Sweden. ISSN 0018–0661. Received October 25, 1983 153 populations of tetraploid and 72 populations of hexaploid wheats collected in Ethiopia from 20 and 17 regions, respectively, were grown in a greenhouse, and 6331 and 2700 individuals of tetraploids and hexaploids were studied for basal spikelet fertility, awn colour, glume colour, glume hairiness, kernel colour, kernel weight, number of tillers, plant height, spike length, number of spikelets per spike, and number of seeds per spike. Analyses of regional patterns of character variation to determine the relative contribution of various regions to germplasm resources showed differences in the level of importance of useful germplasm material. Polymorphism of characters studied is higher in tetraploids. The contribution to the total variation varies among characters. In both tetraploids and hexaploids the contribution to the total phenotypic diversity is highest at the lowest level (within localities), followed by the differences among populations in a region, and among regions. Both tetraploids and hexaploids are assumed to equally rely on phenotypic plasticity in adapting to the multiplicity of environments, and TWINSPAN analysis showed differences in the frequencies of characters prefemng negative and positive groups differentially among the various regions. Combinations of characters showed dissimilarity among regions and between ploidy levels. This may mean particular adaptive strategies through the effect of correlated characters.

Chromosomal localization and copy number of 18S + 28S ribosomal RNA genes in evolutionarily diverse mosquitoes (Diptera, Culicidae).

Abstract: In situ hybridization using 3H-labeled 18S and 28S ribosomal DNA (rDNA) probes from Aedes albopictus was performed on the mitotic chromosomes of 20 species of mosquitoes belonging to 8 genera of subfamilies Culicinae and Anophelinae In all but one species examined, the rDNA family was localized to a single chromosome per haploid genome Aedes triseriatus was the only exception, with the rDNA cistrons present on chromosome 1 and on chromosome 3 The ribosomal RNA genes were located on chromosome 1 in Ae albopictus, Ae aegypti, Ae flavopictus, Ae seatoi, A polynesiensis, Ae alcasidi, Ae annandalei, Ae mascarensis, Ae hendersoni, Ae atropalpus, Ae epactius, Culex pipiens quinquefasciatus, Wyeomyia smithii, and Sabethes cyaneus; chromosome 2 in Ae mediovittatus and Haemagogus equinus; chromosome 3 in Armigeres subalbatus and Tripteroides bambusa; and the heteromorphic X and Y chromosomes in Anopheles quadrimaculatus The variation in the location of ribosomal RNA genes on the different chromosomes and at different positions on the chromosome arm among the mosquito species examined is suggestive of considerable chromosome repatterning through translocations and inversions in the karyotypic evolution of mosquitoes Dot-blot hybridization was used to estimate copy number of rRNA genes; the copy number per haploid genome ranged from 39 +/- 327 in Sa cyaneus to 1023 +/- 6814 in Ae flavopictus

QTL mapping for chlorophyll content in maize

Abstract: In order to explore the genetic basis for chlorophyll content in maize (Zea mays L.), a total of 189 F2 individuals derived from the single cross between the inbred lines A150-3-2 and Mo17 were used as mapping population. Four traits associated with chlorophyll content were measured at the trumpet stage and at the flowering stage. Total 32 QTLs were investigated on all the chromosomes except for chromosomes 6 and 10. There were 24 QTLs located on chromosomes 1, 2, 3, 5, 7, 8, and 9 at the trumpet stage. Six QTLs were investigated for chlorophyll-a content (chla), chlorophyll-b content (chlb), other chlorophyll content (chlc), and total chlorophyll content (chlz), respectively. QTLs for four traits were located in the same marker intervals in many cases. The distance among different QTLs of the four traits in the same marker intervals ranged from 0 to 2 cM. The four major QTLs for chla, chlb, chlc, and chlz at the trumpet stage, which explained 11.63%, 10.3%, 10.77%, and 11.51% of the phenotypic variance, respectively, were investigated between umc1098 and bnlg557 on chromosome 5. There were 8 QTLs located on chromosomes 4 and 5 at the flowering stage, with 2 QTLs for chla, chlb, chlc, and chlz, respectively. QTLs were investigated between umc1098 and bnlg557, which controlled the four chlorophyll content traits (chla, chlb, chlc, and chlz), at the trumpet stage and two chlorophyll content traits (chla and chlb) at the flowering stage. QTLs between umc2308 and bnlg386 for the four traits related to chlorophyll content were investigated only at the flowering stage.

Nucleolus organizer polymorphism in barley, Hordeum vulgare L.

Abstract: Linde-Laursen, 1. 1984. Nucleolus organizer polymorphism in barley, Hordeum vulgare L. —Hereditas 100:3343. Lund, Sweden. ISSN 0018–0661. Received March 28, 1983 Twenty-nine barley lines with the standard karyotype were differentiated by nucleolus organizer (NOR) polymorphisms. In 27 lines chromosome pair 6 had longer secondary constrictions, larger silver nitrate-stained NORs, and formed larger nucleoli than chromosome pair 7. Two lines showed the opposite combination of chromosomes and characters, but had different sizes and “strengths” of nucleolus organizers on chromosome pair 6. One of these lines had a high frequency of interphase cells with micronucleoli suggesting the presence of an extra pair of nucleolus organizers. The heteromor-phisms of NORs are probably due to tandem duplications. The NORs were located in the secondary constrictions and did not comprise adjacent C-bands. The mean nucleolar volumes were the same in representative lines of the three groups of barley and in a translocation line that has both nucleolar organizers in one chromosome arm and shows “intrachromosomal nucleolar dominance”. This suggests the existence of a compensational mechanism for nucleolus formation. Minor silver nitrate-stained bands sometimes developed at both sides of the centromeres. A positive correlation was indicated between the length of a secondary constriction, the size of a NOR, and the nucleolus formed at it. This may be the normal situation in plants.

Increased sister chromatid exchange frequency in lymphocytes in healthy cigarette smokers

Abstract: SCE rates in peripheral lymphocytes may be useful for evaluation of environmental mutagens. Since lung cancer is strongly associated with cigarette smoking, an association of SCE with cigarette smoking might be of interest. Controversy about this question prompted the present study of SCE in peripheral lymphocytes in 149 healthy, unmedicated persons. 60 non-smokers had 8.25 ± 0.13 SCE/cell (mean value ± standard error of the mean), and 89 cigarette smokers had 9.23 ± 0.14 SCE/cell. The sum of SCE in 30 metaphases in each person was transformed to a normally distributed metameter, y= (SCE)½+ (SCE+1)½, which was found to be significantly increased with increasing cigarette consumption. The linear regression calculated for y= (SCE)½+(SCE+1)½ and x=number of cigarettes smoked per day was y=31.43+0.094 x. It was concluded that cigarette smokers have increased SCE in peripheral lymphocytes. The significance of this in respect to risk of development of cancer in the lung is unknown. The influence of cigarette smoking should be considered when using the SCE test principle to evaluate in vivo exposure to potential mutagens.

Genome relationships in the perennial Triticeae based on diploid hybrids and beyond

Abstract: Diploid intergeneric hybrids were synthesized among diploid species of the genera Agropyron Gaertn. (P genome), Pseudoroegneria (Nevski) A. Love (S genome), Thinopyrum A. Love (J-E genome), Psathyro-stachys Nevski (N genome), Hordeum L. (H genome), and Secale L. (R genome). Chromosome pairing patterns in these diploid hybrids permit the estimation of genomic similarity among the various genomes. Measurements of genome similarity based on chromosome pairing in diploid hybrids are generally in agreement with those based on other measurements. It is consistent that Jb and Je (= E) are the most closely-related genomes, with the genetic similarity ranging from 0.50 to 0.68, based on various studies. Next to the Jb-Je genome are S and P genomes. The N, H, and R genomes are remotely related to the J-S-P cluster. These relationships are also reflected in hybrids of higher ploidy levels when genes controlling chromosome pairing are kept in check. Since genome designation is traditionally based on chromosome pairing data and the ability of two genomes to pair without interfering factors is a reliable measurement of genome similarity, diploid pairing data should be used for genome symbol determination. It is logical to set a diploid c value of 0.50 for designating the basis genome symbol; i.e., when the diploid hybrids have a mean c > 0.50, the two genomes in the hybrid should be given the same basic symbol.