bluuebunny/crossref_metadata_2025 huggingface dataset:
Muller's Ratchet and the evolution of supernumerary chromosomes
Authors: Green David M.
Published: April 2011

Supernumerary chromosomes arise from portions of the normal chromosome complement through nondisjunction, fragmentation, or other mechanisms. Once present in the genome, they are subject to virtually the same genetic conditions that affect the evolutionary degeneration of heteromorphic sex chromosomes. Y or W chromosomes occur only in the presence of X or Z chromosomes, respectively, just as supernumeraries never occur except in the presence of the complete regular karyotype containing their progenitor sequences. Thus, mechanisms that can account for the evolution of sex-chromosome heteromorphism can also be invoked to explain the degeneration process of supernumerary chromosomes after their origination. Incipient supernumeraries initially have genes identical with those on progenitor chromosomes. This frees them from the evolutionary constraint of carrying nonduplicated genetic information, just as in Y and W chromosomes during early stages of sex-chromosome differentiation. The degeneration of supernumerary chromosomes may thus proceed via the mechanism of Muller's Ratchet. This hypothesis predicts that supernumerary chromosomes should lose functional loci, lose sequence homology with the regular genome, and gain heterochromatin over time, resulting in multiple heteromorphic forms of degenerate supernumeraries within and between populations, as is commonly observed.Key words: supernumerary chromosomes, B chromosomes, evolution, origin, Muller's Ratchet.
Transcriptional analyses of the uncoordinated region of Drosophila melanogaster
Authors: Healy Marion J. , Russell Robyn J.
Published: April 2011

RNA blotting experiments reveal that a genomic region encompassing the uncoordinated complementation group of Drosophila melanogaster produces two classes of transcripts. The first class contains five polyadenylated RNAs, of 4.35, 8.7, 9.0, 11.5, and 13.0 kb, and the second class contains a transcript of 7.3 kb that can be detected in both the total cellular and the poly(A)+ fractions. Transcripts of the first class are found predominantly in the early larval, pupal, and adult life stages, whereas the 7.3-kb species is present throughout the life cycle and is also found in the heads of adult flies. The two classes of RNAs derive from different combinations of exons. Analyses of RNAs derived from genotypes that are deficient for the uncoordinated complementation group and from seven uncoordinated mutant alleles support the suggestion that the uncoordinated gene (unc) has been isolated and encodes the multiple transcripts.Key words: Drosophila, multiple transcripts, uncoordinated gene, heterochromatin.
Deletion mapping by gametocidal genes in common wheat: position of speltoid suppression (Q) and β-amylase (β-Amy-A2) genes on chromosome 5A
Authors: Tsujimoto H. , Noda K.
Published: April 2011

The genes for speltoid suppression (Q) and β-amylase (β-Amy-A2) in common wheat (Triticum aestivum) were mapped cytologically on the long arm of chromosome 5A by using four 5Aq deletion lines produced by the action of gametocidal genes of Aegilops speltoides. A line with 13% terminal deletion in the whole long arm lacked both β-Amy-A2 and Q, indicating that these genes are confined within the terminal area. According to the genetic map, four other genes distal to β-Amy-A2, B1 (awn suppression), Hn (hairy node), Vrn1 (vernalization), and Kr2 (crossability), must also exist in this 13% terminal area. The β-Amy-A2 gene is mapped at 20 centimorgans (cM) from the centromere, and map distance between β-Amy-A2 and Kr2 is estimated at 97.5 cM. A comparison of the cytological map drawn by the present deletion analysis with the genetic map based on the recombination values indicates that recombination is restricted to the proximal region of chromosome 5A.Key words: Triticum aestivum, gametocidal genes, cytological map, genetic map, deletion mapping.
Abnormal genetic segregation associated with the presence of a Y.w+ chromosome in Drosophila melanogaster
Authors: Rosenberg-Bourgin Myriam , Bracone Annie , Lemeunier Françoise , Aulard Sylvie , Paumard Solange , Contesse Gérard
Published: April 2011

We have observed an abnormal genetic segregation in the progeny of crosses between males of the F71 (y wa/Y.w+) strain and females of various strains carrying marker mutations on their chromosome 2. The Y.w+ chromosome, previously described as possibly being associated with a translocation of the 22D region of chromosome 2, was shown to carry the 21A1–22E4 tip of the 2L chromosome. One chromosome 2 of F71 had a deletion of this region. The abnormal genetic segregation observed in the progeny of different crosses can be explained both by the partial lethality (which becomes severe in some homogeneous genetic backgrounds) due to trisomy of the 21A1–22E4 chromosome 2 fragment and by the lethality associated with monosomy of this 21A1–22E4 segment.Key words: Drosophila, trisomy, segregation distortion.
Location of a Triticum speltoides chromosome segment conferring resistance to leaf rust in Triticum aestivum
Authors: Dvořák J. , Knott D. R.
Published: April 2011

A leaf rust resistant line, 2-9-2, was selected in the fourth backcross generation to Triticum aestivum of an interspecific hybrid, T. aestivum × Triticum speltoides. The resistance segregated independently of T. speltoides leaf rust resistance gene Lr28, previously shown to be incorporated into wheat chromosome 1B in two other transfer lines. Monosomic and telosomic analyses showed that the gene in line 2-9-2, Lr36, was incorporated into the short arm of chromosome 6B. C-banding analysis showed that the homoeologous crossing-over occurred distally to an interstitial C-band in the satellite and linkage analysis showed Lr36 to be tightly linked to the telomeric C-band.Key words: C-banding, physical mapping, linkage, wheat, chromosome 6B, introgression.
Localization of the 5S RNA genes to arm 2R in polytene chromosomes of Lucilia cuprina (Diptera: Calliphoridae)
Authors: Bedo D. G. , Webb G. C.
Published: April 2011

The 5S RNA genes of Lucilia cuprina were mapped to section 15A in the short arm of chromosome 2 by in situ hybridization to pupal trichogen polytene cells. As in most eukaryotes the 5S genes are located separately from the remaining ribosomal RNA genes.Key words: Lucilia cuprina, 5S RNA, in situ hybridization.
Stability at the phosphoglucoisomerase (PGI/2) locus in Festuca arundinacea plants regenerated from cell suspension and protoplast culture
Authors: Humphreys M. W. , Dalton S. J.
Published: April 2011

A study was made of the phosphoglucoisomerase (PGI/2) phenotype of plants regenerated from suspension and protoplast culture originating from a Festuca arundinacea (2n = 6x = 42) plant with distinct PGI/2 phenotype. Of the regenerated plants from suspension culture, 20 were abnormal in that they deviated from the PGI/2 phenotype of the donor plant. Among the abnormal plants two distinct isozyme variants absent in the original donor, which were probably the result of point mutations, were recorded. There was evidence of deletions of specific PGI/2 alleles. This was confirmed cytologically by the reduced chromosome number found in the relevant cell suspension derived plants. There was also evidence that an active allele had been transformed into a null allele. All the plants regenerated from protoplast culture had the same PGI/2 phenotype as the donor plant but were hyperpolyploid. The loss of activity of individual PGI/2 alleles in plants derived from protoplasts was masked by gene duplication because of their hyperpolyploid nature. A high degree of instability was identified in nonregenerating calli. It was thought that abnormalities in the nonregenerating calli were affecting their potential to regenerate plants.Key words: Festuca arundinacea, somaclonal variation, phosphoglucoisomerase (PGI/2), chromosome instability, point mutations.
Synapsis and chiasma formation in a ditelo-substituted haploid of rye
Authors: Jong J. H. de , Havekes F. , Roca A. , Naranjo T.
Published: April 2011

Synapsis and chiasma formation were analyzed in a ditelo-substituted haploid of rye (Secale cereale), in which chromosome 1R was replaced by its telosomes. The study was made by comparing synaptonemal complex formation at early meiotic prophase I, chromosome associations at metaphase I, and recombinant chromosomes at anaphase I and prophase II. For the analysis of synaptonemal complexes, 41 nuclei at stages ranging from leptotene to early diplotene were selected. In the leptotene and early zygotene nuclei, numerous alignments of axial cores involving the same or different chromosomes were observed. Pairing initiation sites occurred at both interstitial and distal segments. Throughout zygotene the extent of pairing gradually increases, with values up to 84.8% at a stage that is morphologically comparable with late pachytene. Pairing-partner exchanges were frequently observed in zygotene nuclei, giving rise to multiple associations encompassing all or most of the chromosomes. In cells at metaphase I multivalents were very rare (2%), indicating elimination of most pairing-partner exchanges. In cells at metaphase I, anaphase I, and prophase II chromosome length, centromere position, and C-banding pattern enable the identification of the chromosomes 1RS, 1RL, 4R, 5R, and 6R, and the distinction of three metacentric chromosomes (RM1, RM2, and RM3). Metaphase I bonds were found to be nonrandomly distributed. Associations between the arms 4RL, 5RL, 6RL, and RM1L, all of them without telomeric C-bands, were more frequent than between the remaining arms. The bonds were mainly located at the distal parts of the chromosomes. The frequency of recombinant chromosomes at anaphase I or prophase II suggests that metaphase I bonds were true chiasmata.Key words: Secale cereale, haploid, synaptonemal complex, chiasmate bonds, C-banding.
Synaptic mutants in potato, Solanum tuberosum L. III. Effect of the Ds-1/ds-1 locus (desynapsis) on genetic recombination in male and female meiosis
Authors: Jongedijk E. , Hutten R. C. B. , Wolk J. M. A. S. A. van der , Stekhoven S. I. J. Schuurmans
Published: April 2011

By applying half-tetrad analysis to segregating tetraploid progeny that had been raised from 2x–4x and 2x–2x crosses, five marker loci (ym, y, Got-1, Got-2, and ds-1) were mapped to their respective centromeres in male and female meiosis of both normal synaptic and desynaptic (ds-1ds-1) diploid potato clones. Significant sex differences in genetic recombination for these loci did not occur in either normal plants or desynaptic mutants, which suggests that genetic exchange in both the sexes is governed by the same control system. In desynaptic mutants a severe reduction in crossing-over was observed for ym and.y (83.7 an 90.0% reduction, respectively), whereas recombination rates for Got-2 appeared to have systematically, although not significantly, increased. The ds-1 gene was concluded to substantially reduce the overall chiasma frequency and to differentially alter chiasma distribution along individual chromosomes. Based on segregation ratios in progeny from different types of testcrosses, first division restitution (FDR) and second division restitution (SDR) 2n gametes formed by normal synaptic plants were estimated to transmit on average about 82.7 and 36.1 %, respectively, of the parental heterozygosity to tetraploids. With desynapsis the average amount of heterozygosity transmitted by FDR 2n gametes amounted to 94.1%. SDR 2n gametes from desynaptic mutants are sterile as a result of aneuploidy. The ds-1 gene was demonstrated to particularly enhance the ability of FDR 2n gametes to preserve the genetic constitution of diploid parental clones with a minimum amount of reassortment. The potential value and limitations of the ds-1 gene for the production of true potato seed varieties and the experimental induction of diplosporic apomixis are discussed.Key words: Solanum, genetic markers, gene–centromere mapping, desynapsis, reduced recombination.
Regularities of in situ nick translation labeling pattern of cereal metaphase chromosomes
Authors: Kost M. V. , Bolsheva N. L. , Badaev N. S. , Zelenin A. V.
Published: April 2011

A method of nick translation in situ that makes it possible to detect regions hypersensitive to DNase I in metaphase chromosomes has been modified for plants. Such regions have a peculiar structural conformation typical of transcriptionally active chromatin. The distribution of transcriptionally active regions labeled with [3H]TTP along the length of individual chromosomes of rye and B genome of wheat was studied. The following regularities of this distribution were found: a weak labeling of heterochromatic regions; an increase in the intensity of labeling in regions located at the border of euchromatin and heterochromatin and in the nucleolar organizer regions. Each chromosome of the B and R genomes has its own labeling pattern, but some similarities in the labeling pattern in all chromosomes have been revealed. Such similarities are characteristic of homoeologous chromosomes.Key words: wheat, modified nick translation, rye.
Evolution of genome size in darkling beetles (Tenebrionidae, Coleoptera)
Authors: Juan C. , Petitpierre E.
Published: April 2011

Thirty-seven species of tenebrionid beetles from mainland Spain and the Balearic Islands and Canary Islands have been surveyed for nuclear DNA content of Feulgen-stained spermatids. The range of 1C genome sizes among 44 species checked to date is relatively moderate at nearly fivefold, from 0.18 to 0.86 pg, with an average value of 0.36 pg, but it contrasts with the small range of chromosome numbers in these beetles. Highly significant correlations (p < 0.001) between genome size and either spermatid area or whole metaphase I chromosomal area were found in these species. Moreover, their nuclear DNA content also correlated significantly (p < 0.05) with diploid chromosome number. A striking difference between the average DNA content of Tentyriinae and Tenebrionidae was also detected, that of the Tentyriinae being clearly smaller. A possible trend towards decrease in genome size could possibly explain most of evolutionary divergence in Tenebrionidae except for Blaps and some Opatrini, which have probably undergone substantial increases of nuclear DNA content.Key words: genome size, Tenebrionidae, evolution.
TaqI digestion reveals fractions of satellite DNAs on human chromosomes
Authors: Tagarro I. , González-Aguilera J. J. , Fernández-Peralta A. Ma
Published: April 2011

Restriction endonuclease TaqI has been known as a nonbanding restriction endonuclease when it is used on fixed human chromosomes. However, a specific TaqI digestion can be obtained after varying experimental conditions such as concentration of enzyme, time of incubation, and volume of the final reaction mixture. This digestion consists of an extensive DNA loss in heterochromatin subregions of chromosomes 1, 9, 15, 16, and Y. These regions essentially coincide with those corresponding to the main chromosome locations of satellite II DNA, whose tandem repeated units contain many TaqI target sequences, and some satellite III DNA domains enriched in TaqI sites.Key words: TaqI restriction endonuclease, heterochromatin, satellite DNAs, human chromosomes.
Comparison of mitochondrial DNA sequences of seven morphospecies of black flies (Diptera: Simuliidae)
Authors: Xiong Bai , Kocher Thomas D.
Published: April 2011

Universal primers constructed from the 16S ribosomal RNA gene in the Drosophila yakuba mitochondrial genome were successfully used to amplify, via the polymerase chain reaction, the homologous region of mitochondrial DNA from seven black fly morphospecies. Amplification was achieved from single larval salivary glands and from single adults preserved in Carnoy's fixative (ethanol – acetic acid, 3:1), allowing DNA sequences and polytene chromosome banding pattern data to be gathered from the same individuals. Nucleotide sequences of the amplified DNA segment (347 base pairs) were obtained from all the species examined. As in Drosophila, the nucleotide base composition of the sequenced segment from black flies had a high adenine (A) and thymine (T) content (A + T on average comprised 77% of all nucleotides.). Nucleotide differences among the seven species were observed at 59 positions (55 nucleotide substitutions and 4 deletions). There were more transversion differences than transition differences both among and within genera; the proportion of transversions was higher between genera than within genera. Most transversion differences were A ↔ T type, comprising 79% of all transversion differences and 50% of all sequence differences. Phylogenetic inference based strictly on transversion differences confirmed traditional generic and tribal groupings, i.e., Prosimulium fuscum (Syme &Davies) is close to Prosimulium magnum (Dyar &Shannon); Simulium decorum (Walker), Simulium venustum s.l. (Say), and Simulium vittatum s.l. (Zetterstedt) are close to each other; Stegopterna mutata (Malloch) and Cnephia dacotensis (Dyar &Shannon), which belong to the tribe Cnephiini, are grouped together.Key words: polymerase chain reaction, mitochondrial DNA, polytene chromosomes, phylogeny, black flies.
Cytogenetic studies on a heterozygous reciprocal translocation in the wheat (Triticum aestivum) cultivar Atlas 66
Authors: Primard Sandra J. , Morris Rosalind , Papa Charles M.
Published: April 2011

The wheat (Triticum aestivum L.) cultivar Atlas 66 possesses a heterozygous reciprocal translocation that has persisted through seven generations of self-pollination and also has appeared in progeny of crosses between cv. Atlas 66 and other wheat cultivars or lines. Crosses were made between cv. Atlas 66 and the 21 cv. Chinese Spring double ditelosomics to identify the chromosomes involved in the translocation. F1 plants testing chromosomes 2A and 2D had a chain with one telosome attached and the other unpaired in some metaphase I cells, indicating that 2A and 2D were involved in the translocation. The F1s testing the other 19 chromosomes had a chain of four and a trivalent that included the two telosomes. F1 meiotic configurations from crosses between cv. Altas 66 and cv. Chinese Spring ditelosomics 2AS, 2AL, 2DS, and 2DL indicated that the breakpoints were in 2AL and 2DL and that the breakpoint in 2DL was closer to the end of the arm than the breakpoint in 2AL. The short translocated 2DL segment could explain the occurrence of chains as well as rings when cv. Atlas 66 was self-pollinated, and a predominance of chains in crosses with other cultivars or lines. There was evidence for the transmission of duplicate-deficient gametes from the translocation.Key words: heterozygous reciprocal translocation, Triticum aestivum, wheat, cv. Atlas 66.
Genomic composition of 4x–2x potato hybrids: influence of Solanum chacoense
Authors: Bani-Aameur Fouzia , Lauer F. I. , Veilleux R. E. , Hilali A.
Published: April 2011

Tetraploid potato hybrids representing three genomic compositions (TTTT, TTPP, and TTPC (T, Solanum tuberosum; P, Solanum phureja; C, Solanum chacoense)) were constructed by crossing S. tuberosum (2n = 4x = 48) cultivars or advanced breeding selections among themselves or with 2n pollen producing selections of either S. phureja (2n = 2x = 24) or F1 hybrids between S. phureja and S. chacoense (2n = 2x = 24). Seedling families were evaluated in the fall season and selections within each family were evaluated in spring trials at Ait-Melloul, Morocco. Genomic composition was the greatest source of variance for yield-attributing traits, with TTPC outperforming other hybrids in fall trials for vine vigor, tuber set, and tuber yield and TTPP outperforming other hybrids in spring trials for the same traits. The results imply that analytic breeding for potato by construction of complex interspecific hybrids may result in clones surpassing a previously proposed heterotic threshold if the target environment is conducive to expression of favorable traits from alien germ plasm.Key words: Solanum phureja, Solanum chacoense, Solanum tuberosum, 4x–2x hybrids, potato, analytic breeding.
The interspersed DNA repeat conserved in water birds' genomes
Authors: Zhu X. , Burgoyne L. A. , Skinner J. D.
Published: April 2011

A putative old and ubiquitous interspersed DNA repeat family was identified from TaqI restriction, M13 cloning, and sequencing of the genomic DNA of a Mallard (Anas platyrhynchos), a Muscovy Duck (Cairina moschata), a Toulouse Goose (Anser anser), and a Black Swan (Cygnus atratus). A 425-bp consensus core sequence was obtained for the interspersed family. The 425-bp unit was about 2% of the avian genome and was found to be conserved in at least four genera of the order Anseriforme: Anas, Anser, Cairina, and Cygnus.Key words: avian, bird, interspersed repetitive DNA.
Unusual chromosome separation in meiosis of Cuscuta L.
Authors: Pazy Batia , Plitmann Uzi
Published: April 2011

This study suggests that precocious division of centromeres and probably inverted meiosis (i.e., the rare occasion in meiosis when the equatorial division precedes the reductional division) occur not only in Cuscuta babylonica Choisy but also in several other dodders, regardless of their chromosome number. It was found in four additional species, all of which belong to subgenus Cuscuta. At least two other species (of subgenus Grammica and subgenus Monogyna) undergo the usual process. Therefore, Cuscuta warrants closer study and may provide a better understanding of inverted meiosis as well as the regular process of meiosis.Key words: inverted meiosis, precocious division of centromere, Cuscuta spp.
Segmental duplication of distal chromosomal regions in maize
Authors: Carlson Wayne R. , Roseman Robin R.
Published: April 2011

A number of cytogenetic methods have been used to duplicate specific chromosomal segments in maize. However, most of these techniques do not produce heritably stable duplications. The absence of stable inheritance for a duplication means that stock maintenance is difficult and potential agricultural applications cannot be pursued. Two methods for producing stable segmental duplications in maize have been previously proposed. Both methods utilize translocations between the maize B chromosome and standard chromosomes (B–A translocations). One technique duplicates proximal chromosomal segments, while the other duplicates distal regions. The proximal-duplication method was tested earlier. The distal-duplication technique is analyzed here. Two homozygous distal duplications were constructed and tested for gametic transmission. The duplications were found to be heritably stable within the limits of the genetic and cytological tests that were employed.Key words: B chromosome, maize, duplication.
A cytogenetic comparison of some North American owl species
Authors: Schmutz Sheila M. , Moker Jane S.
Published: April 2011

Karyotypes of three owl species previously not reported, the Burrowing Owl (Athene cunnicularia), the Hawk Owl (Surnia ulula), and the Western Screech Owl (Otus kennicotti), are presented. Comparison with other karyotypes in the literature suggests that the Burrowing Owl should be in a separate genus, as was previously the case. The Hawk Owl karyotype was found to bear considerable similarity to some Athene species, although we are not suggesting they should be placed in one genus. The karyotype of the Western Screech Owl appears to have diverged from the Otus species described previously, but these chromosomal data are not incompatible with these species sharing a common genus. A karyotype of the Long-eared Owl, which differs slightly from a previously published version, is presented. Relationships among the owls karyotyped to date are discussed on the basis of cladistic interpretations of these data.Key words: Strigiformes, phylogeny, karyotype, evolution, chromosome.
Synaptonemal complexes of triploid (ZZW) chickens: Z–Z pairing predominates over Z–W pairing
Authors: Solari Alberto J. , Thorne M. H. , Sheldon B. L. , Gillies C. B.
Published: April 2011

Twelve triploid, ZZW chickens of ages ranging from day 19 of incubation to 15 days after hatching were used for oocyte analysis. Oocytes show 117 axes per nucleus. At early pachytene, most axes form double synaptonemal complexes (triplets). An average of 27 triplets, 12 bivalents, and 12 univalents was observed. Later, a partial elimination of triplets occurs, as they are converted into typical trivalents or bivalents and univalents. The number of recombination nodules per nucleus (52.7) is similar to that of diploids. These nodules can occur in register in both central regions of a triplet (no lateral interference), and they probably stabilize the central region. Among 31 oocytes, 29 had a regular ZZ bivalent and a W univalent, and only 2 had triple pairing between a ZZ bivalent and a terminal region of the W axis (less than 1 μm in length and having a terminal recombination nodule). Competition for pairing between the gonosomes results in a large (93.5% of cases) predominance of Z–Z pairing, because of a relatively minor homology between the W and Z chromosomes. The prevailing pairing failure of the W chromosome may lead to early oocyte loss.Key words: sex chromosomes, triploids, synaptonemal complex, Z–W pairing, chicken, recombination nodules.
Incorporation of restoring gene of Aegilops umbellulata into wheat
Authors: Ma Zheng-Qiang , Zhao Yin-Hai , Liu Da-Jun
Published: April 2011

Six 'Chinese Spring' – Aegilops umbellulata Zhuk. addition lines (UAD, UBD, UCD, UDD, UED, and UFM) were assayed for their effects on the fertility of timopheevi cytoplasm male sterile lines (T-type). Chromosome 6U of disomic addition line UAD was found to be able to restore the fertility of T-type male sterility and 'Chinese Spring' was verified to lack restoring genes, indicating that 6U carries at least one fertility restoration gene. From about 200 plants with 42 somatic chromosomes derived from the progeny of crosses Qu Xian Early A × UAD and Sumai No. 3 A × UAD, eight self-fertile plants were selected. Their self-fertility in timopheevi cytoplasm implies that they carry the restoring gene(s) from 6U. Cytological analysis was conducted on the hybrid F1 of the selected fertile plants (040-5, 060-1, and 061-4) as female parents crossed with 'Chinese Spring'. The self-fertility segregation and the chromosome pairing of pollen mother cells of F1 fertile plants from 040-5, 060-1, and 061-4 × 'Chinese Spring' during meiosis suggested that they were heterozygous translocation lines with restoring gene(s) from 6U.Key words: Aegilops umbellulata Zhuk., restoring genes, alien gene transfer, timopheevi cytoplasmic male sterile fertility, Triticum aestivum L.
Instability of the blue grain color in a strain of Triticum aestivum L.
Authors: Mettin D. , Schlegel G. , Lehmann Chr.
Published: April 2011

The blue-grained wheat accession TRI 2401 (Triticum aestivum var. tschermakianum Mansf.) from the gene bank in Gatersleben was confirmed to be an alien disomic substitution for wheat chromosome 4Aa, which confers blue aleurone. Reciprocal hybrids with 'Chinese Spring' had nonblue (red) seeds in F1 and segregated on average 74% nonblue and 26% blue in F2. This segregation is not necessarily monogenic. In selfed progeny of TRI 2401 about 1.4% of the seeds were nonblue (red). Most of these aberrant seeds were monosomic for the alien chromosome. The seed from selfing of the monosomics segregated in a ratio of 67% nonblue (2n = 41) to 33% blue (2n = 42). The nonblue seeds undoubtedly arose from aneuploid gametes originating by nondisjunction during gametogenesis. Since 20-chromosome male gametes rarely function, it was assumed that the deficiency was mostly transmitted through the egg cells. In addition, spotting of the blue aleurone was observed with a frequency of 0.017%. Size and pattern of the spots varied considerably. It is thus likely that the loss of the blue color in the aleurone cells resulted from the loss of the alien chromosome during endosperm development. On the basis of the behavior mentioned, it was concluded that the gene(s) for blue aleurone in the European wheat accession TRI 2401 seem to be different from the analogous gene, Ba, in the blue-grained derivatives of wheat × Elytrigia pontica crosses.Key words: Triticum aestivum var. tschermakianum, blue aleurone, 4Aa substitution, color spots.
DNA amplification, chromatin variations, and polytene chromosomes in differentiating cells of common bread wheat in vitro and roots of regenerated plants in vivo
Authors: Shang Xiao Min , Wang Wen Chung
Published: April 2011

Polytene chromosomes and giant nuclei were observed in differentiating cells of embryogenic calli and root tips of wheat plants (Triticum aestivum cv. Mustang) regenerated from long-term cell suspension cultures and selected cell lines after high-temperature stress. Many giant nuclei almost completely occupied the cellular space of the large parenchyma cells. The amount of DNA from the giant nuclei was as high as 174 C, equivalent to 3.03 × 104 pg of DNA, as revealed by Feulgen cytophotometry. Following cell differentiation, the giant nuclei that were endoaneupolyploid and polytene developed from interphase nuclei (aneuploid) and micronuclei. Polytene chromosomes from the B genome were tentatively identified by their banding patterns, as shown by the HCl–KOH–Giemsa banding method. Variations of polytene chromosomes were cable-like, dispersed, heterochromatinizated, or granulated at the different developmental stages. The number of granular chromatin particles in the cells was 85 to more than 300 when disintegration of the giant nuclei occurred. Some were exclusively heterochromatic, and many others consisted of both euchromatin and heterochromatin. The amount of DNA for these granular chromatin particles was estimated from 0.17 to 5.54 pg. Many minutes and double minutes existed in various stages of dividing and differentiating cells and accompanied the generation and disintegration of the giant nuclei. The DNA sizes of these minutes were estimated as 2.56 × 105 – 1.05 × 107 bp. These results suggested that DNA amplification, polytene chromosomes, minutes, and double minutes were induced in polyploid species with large chromosomes and maintained in embryogenic calli in vitro and apical segments of root tips of regenerated plants in vivo.Key words: giant nucleus, endoaneupolyploidy, polyteny, minutes and double minutes, cell differentiation, Triticum aestivum.
Standard karyotype and nomenclature system for description of chromosome bands and structural aberrations in wheat (Triticum aestivum)
Authors: Gill B. S. , Friebe B. , Endo T. R.
Published: April 2011

A standard karyotype based on N-banding, C-banding, and modified C-banding has been constructed for Triticum aestivum L. 'Chinese Spring'. An idiogram and a nomenclature system have been developed for the description of individual bands. Nomenclatural rules have been proposed for the description of chromosomal structural aberrations and polymorphic bands in other wheat cultivars. As a rule each short arm (S) and a long arm (L) consists of a series of dark bands (C-bands) and light bands (mainly euchromatic) and by definition there are no interbands. In some cases, each arm has been subdivided into two or more regions. The description of a band requires designation of a chromosome number, arm (S or L), region, and band. The region number is separated from the band number by a decimal point. Except for arms 1AS, 3AL, 4AS, and 6AS, all wheat chromosome arms have one or more intercalary C-bands and are divisible into three or more bands. It is hoped that the proposed karyotype and nomenclature system will be widely adopted and lay the foundation of definitive chromosome analysis in wheat.Key words: C-banding, N-banding, common wheat, heterochromatin, idiogram.
Para-Fluorophenylalanine-induced chromosome number changes in higher plants. II. Tomato and rape
Authors: Banks P. , Britten E. J. , Gordon G. H.
Published: April 2011

Germinating seeds of rape (Brassica napus L.) and of tomato (Lycopersicon esculentum Mill.), and 1-month-old tomato seedlings, were treated with para-fluorophenylalanine to change chromosome numbers. A number of morphological aberrations were found in treated plants of both species, some of which were also observed in progeny of treated tomatoes. Aneuploids and polyploids were confirmed cytologically in treated plants of both species. The investigations confirm the suggestion previously made for maize, that para-fluorophenylalanine is capable of changing chromosome numbers and the resulting morphology of plants of widely different phylogenetic categories.Key words: Para-fluorophenylalanine, chromosome number changes, plants, tomato, rape, aneuploids, polyploids, morphological changes.
The expression of temperature-stress proteins in a desert cactus (Opuntia ficus indica)
Authors: Somers Daryl J. , Giroux Randal W. , Filion W. Gary
Published: April 2011

Opuntia ficus indica roots grown hydroponically at 20 or 30 °C were subjected to a range of heat-shock temperatures as high as 50 °C for 2 h. Roots grown at 30 °C sustained a greater level of total protein synthesis than did 20 °C-grown roots following heat-shock treatments ≥ 45 °C. The 30 °C-grown roots synthesized 31 families of heat-shock proteins between 38 and 47 °C in comparison with 20 °C-grown roots, which synthesized 19 families of heat-shock proteins at 45 °C. In both groups of roots, the heat-shock response was dominated equally by the 71–75 and a 62 kDa heat-shock protein families. In addition, the 20 °C-grown roots expressed 11 families of cold-shock proteins following 2 h at 4 °C, five of which had similar relative molecular masses to heat-shock protein families. There were numerous qualitative differences in the heat shock protein profiles between the roots grown at 20 and 30 °C; the 30 °C-grown roots expressed several unique heat shock protein families.Key words: heat-shock protein(s), cactus, thermal stress, acclimation.
Homology of chromosomes of the X genomes in common and Uruguayan dallisgrass, Paspalum dilatatum
Authors: Burson Byron L.
Published: April 2011

Two biotypes of dallisgrass, Paspalum dilatatum Poir., designated common and Uruguayan, have chromosome numbers and genome formulas of 2n = 5x = 50 (IIJJX) and 2n = 6x = 60 (IIJJXX), respectively. The relationship between the X genomes in these two biotypes is unknown, and each was arbitrarily assigned the letter X to designate an unknown genome. This study was undertaken to determine the relationship between the X genomes in these two biotypes. Because both biotypes are apomicts and cannot be crossed, a sexual intraspecific F1 hybrid (2n = 45) between sexual yellow-anthered (2n = 4x = 40; IIJJ) and common dallisgrass biotypes was crossed with Uruguayan dallisgrass. This F1 hybrid has complete sets of the I and J genomes but only 5 of the 10 chromosomes of the X genome from common dallisgrass. Two hybrids were recovered. One had 52 and the other had 53 chromosomes, which associated at metaphase I as 22 bivalents + 8 univalents and 23 bivalents + 7 univalents, respectively. Twenty bivalents represent pairing of members of the I and J genomes, and those in excess of 20 represent pairing between members of the two X genomes. The remaining members of the X genome from the Uruguayan biotype were present as univalents at metaphase I. This demonstrates that those chromosomes of the X genome from the common biotype that were present are homologous to members of the X genome of the Uruguayan biotype. Both hybrids are aposporous facultative apomicts with some sterility.Key words: meiosis, intraspecific hybridization, chromosome pairing, genome relations, apomixis.
Production and cytological studies of nine-paired barley (Hordeum vulgare)
Authors: Hang A. , Tsuchiya T.
Published: April 2011

Several barley plants with 2n = 18 chromosomes (9 II) were developed from crosses between two lines with 2n = 16 chromosomes (8 II). Cytological studies of the 18-chromosome plants showed nine bivalents at metaphase I and normal 9:9 segregation at anaphase I. Morphologically, these plants with 18 chromosomes were qualitatively similar to normal diploids (2n = 14), in spite of a duplication of a small proximal segment of the short arm of chromosome 3. However, the 18-chromosome plants were as vigorous as some normal diploid cultivars and more vigorous than 16-chromosome parental lines. If the duplicated segment carried beneficial gene(s), it might be useful for enhancement of germplasm in barley genetics and breeding. The significance of the establishment of this new 18-chromosome barley in karyotype evolution is discussed.Key words: nine-paired barley, aneuploid, trisomic, duplication, Hordeum.
Genetic analysis by use of potato haploid populations
Authors: Kotch George P. , Ortiz Rodomiro , Peloquin S. J.
Published: April 2011

A total of 522 haploids were obtained from six 4x parents. They were used to analyze the genetics of total tuber yield (TTY), average tuber weight (ATW), number of tubers in two hills (NTP), specific gravity (SG), tuber dormancy (TD), vine maturity (VM), after-harvest glucose ratings (GRH), and after-storage glucose ratings (GRS). The analysis of frequency distribution for each trait in the haploid populations provided a means of estimating the main type of gene action, the genetic load for different traits, and the genotypic differences among the parents for these traits. The genetics of the traits was determined by comparing the value of haploid families ("living gametes") to that of their 4x parents. SG and TD represent traits in which additive effects were important. Both additive and nonadditive effects were important in VM, NTP, GRH. TTY, ATW, and GRS were traits in which nonadditive effects were very important. The main type of gene action estimated for TTY and ATW indicates the importance of heterozygosity and epistasis. The reduction in TTY and ATW in haploid populations with respect to the 4x parents was adequately explained as a result of loss of intra- and inter-locus interactions rather than a result of the genetic load of the 4x parents.Key words: maternal haploids, genetic load, epistasis, heterozygosity, quantitative genetics.
A comprehensive study of genic variation in natural populations of Drosophila melanogaster. V. Structural–functional constraints on protein molecules and enzymes and the levels and patterns of variation among genes
Authors: Singh Rama S.
Published: April 2011

Ever since isozyme–allozyme polymorphisms were detected there has been an incessant effort to relate the amount of observed protein variation to various aspects of molecular structure and function. Structural–functional constraints can limit the amount of overall genie variation, and the observed variation can be due to neutral mutation and random genetic drift, mutation–selection balance, or balancing selection. The present analysis of structural–functional constraints on gene–enzyme variation in natural populations of Drosophila melanogaster shows that while both subunit size and substrate group show significant effects on number of alleles and mean heterozygosity, only substrate group affects population structure significantly. Subunit structure (monomer vs. multimer), IUB enzyme class (e.g., tranferase, lyase), and tolerance of null alleles showed no significant effect on level or pattern of variation. While partly interdependent these results suggest that efforts should be made to distinguish between constraints arising from molecular structure and physiological function.Key words: structural–functional constraints, subunit size, gene-enzyme variation, selection, neutrality.
Isolation of three novel Drosophila melanogaster genes containing repetitive sequences rich in GCN triplets
Authors: Magoulas Charalambos , Hickey Donal A.
Published: April 2011

Several cDNA and genomic clones were isolated from Drosophila melanogaster gene libraries by hybridization with a region of a mammalian gene that contains a simple repetitive sequence of six GCN repeats. One of the cDNA clones, E6, was completely sequenced and it was shown that it contains a region of 16 GCN repeats; these repeats encode a polyalanine stretch within a long open reading frame. The sequencing of three different genomic clones (A, B, and D) revealed that all the isolated Drosophila clones are similar to one another in a short region containing variable numbers of the GCN repeat. The genomic clone B was found to be the genomic counterpart of the cDNA clone E6. The other genomic clones, A and D, also hybridize with Drosophila cDNA clones at high stringency. These results indicate that the short GCN repetitive sequences, which we have named ala, are found within transcribed regions of the Drosophila genome. These Drosophila genes containing the ala repeat do not show significant sequence similarity to any presently known gene; we have named these novel genes ala-A, ala-B, and ala-D. The cDNA clone from gene ala-B was named ala-E6.Key words: Drosophila melanogaster, repetitive DNA, GCN repeats, polyalanine encoded domain.
Changes in DNA content and chromosome number during spermatogenesis in the gall midge Monarthropalpus buxi (Cecidomyiidae, Diptera)
Authors: Jazdowska-Zagrodzinska B. , Dallai R. , Redi C. A.
Published: April 2011

In this paper we analyze the course of spermatogenesis in Monarthropalpus buxi. The first meiotic division occurs without any chromosomes pairing. As a result one spermatocyte II appears from which two sperms originate, and one residual cell, which does not undergo any further division. We found variations in chromosome number and DNA content between germ line cells of different individuals. Such variations were observed in the spermatocytes I and II, and in the sperms. In contrast, the residual cells, which did not take part in further development, always had the same DNA content and constantly inherited 20 chromosomes: 4 constituting one haploid set of the somatic type (S chromosomes) and 16 of the germ line limited type (E chromosomes).Key words: DNA content, chromosome number, Cecidomyiidae, germ line, spermatogenesis.
Congruence between genetic, morphometric, and physiological data on differentiation of Turkish chestnut (Castanea sativa)
Authors: Villani F. , Pigliucci M. , Lauteri M. , Cherubini M. , Sun O.
Published: April 2011

Patterns of variability of genetic, morphometric, and physiological traits in Turkish chestnut (Castanea sativa Mill.) are investigated. Previous studies suggested a marked genetic differentiation of Turkish demes, arranged in an east-west cline. Genetic distances based on 21 isozyme loci, discriminant analysis of 13 fruit traits, and analysis of variance of carbon isotope discrimination were carried out. The results agree with genetic divergence reported earlier, and reveal remarkably consistent variation patterns for the three types of biological traits. Historical and anthropogenic effects are discussed as causes of chestnut evolution after the Wurm glaciation and of chestnut dispersal in historical times. Particular attention is focused on probable selective forces that molded the phenotypic variation of C. sativa and lead to the observed similarity of patterns of genetic and morphophysiological levels of variation.Key words: Castanea sativa, isozymes, morphometries, carbon isotype discrimination.
Nucleolar fragmentation in polytene trichogen cells of Lucilia cuprina and Chrysomya bezziana (Diptera: Calliphoridae)
Authors: Bedo D. G.
Published: April 2011

The location of genes coding for 18S and 28S ribosomal RNA in mitotic and polytene cells of Lucilia cuprina and Chrysomya bezziana was investigated using in situ hybridization of an 18 + 28S ribosomal gene probe and silver staining. In both species ribosomal genes were localized to secondary constriction regions in sex chromosome heterochromatin. In L. cuprina mitotic cells the probe hybridizes to a distal secondary constriction region in the short arms of the X and Y chromosomes. In C. bezziana mitotic chromosomes ribosomal genes were located in distal secondary constriction regions in the long arms of the X and Y chromosomes. In polytene trichogen cells of both species, hybridization results varied with the level of polyteny. Cells of low polyteny have a single hybridization site, but with greater polytenization, increasing numbers of extrachromosomal fragments strongly hybridize to the ribosomal gene probe. No hybridization occurs in structures representing the sex chromosomes or in the autosomes. These results indicate that fragmentation and dispersal of the nucleolus occurs during polytenization. Silver staining of both unsquashed and squashed polytene nuclei show identical behaviour of multiple, varied-sized nucleolar bodies, thus confirming the in situ hybridization results. Uridine incorporation studies in L. cuprina indicate that transcription occurs in extrachromosomal bodies similar to nucleolar fragments. Nucleolar fragmentation is more pronounced in L. cuprina males, particularly in those with the translocation T(Y;2)540. Chromosomally normal C. bezziana show nucleolar fragmentation levels similar to that in L. cuprina males. Ribosomal genes are disproportionately replicated in trichogen cells to a much greater extent than surrounding heterochromatin. Nucleolar fragmentation may be a gene amplification system, but it is not known to what degree, relative to diploid amounts, ribosomal genes replicate in trichogen cells.Key words: Lucilia cuprina, Chrysomya bezziana, polytene cells, ribosomal genes, nucleolar fragmentation, disproportionate replication, heterochromatin.
A polytene chromosome study of four populations of Anopheles aquasalis from Venezuela
Authors: Perez Alba Moncada , Conn Jan
Published: April 2011

Polytene chromosome studies were undertaken to elucidate taxonomic relationships among populations of Anopheles aquasalis and A. emilianus in Venezuela. Four collection sites were chosen: two in Sucre state (Santa Fe and Guayana) where A. aquasalis (considered to be A. emilianus by Gabaldón and Escalante) is presumed to be the major regional vector of Plasmodium vivax; and two in areas where no malaria transmission occurs (Caño Rico, Aragua state, and Puerto Cabello, Carabobo state). The chromosome banding pattern of the four populations was identical and conformed to the standard chromosome map of A. aquasalis from Brazil. These results suggest that the population from Santa Fe and Guayana, considered to be A. emilianus, is conspecific with A. aquasalis. However, its status as a distinct species with a homosequential polytene chromosome banding pattern cannot be ruled out.Key words: polytene chromosomes, Anopheles aquasalis, malaria, chromosome banding.
Chromosomal synapsis and the meiotic process in male mesquite lizards, Sceloporus grammicus complex
Authors: Reed Kent M. , Sites Jr. Jack W. , Greenbaum Ira F.
Published: April 2011

Meiosis in males of the F5 cytotype of Sceloporus grammicus was examined through the analysis of synaptonemal complexes (SCs), diakinetic (metaphase I) nuclei, and secondary spermatocytes (metaphase II configurations). These data allowed the establishment of criteria for substaging of zygonema and pachynema, morphological characterization of the SC complement, and comparison of the orientation and segregation of the autosomes and sex chromosomes. The analysis of nuclei from all stages of meiotic prophase I (leptonema through diakinesis) provided a useful means of partitioning the temporal sequence of early meiotic events. Three substages of zygonema (Z1–Z3) were established, based on the extent of synapsis of the microchromosomal and macrochromosomal elements. Synaptic initiation of the autosomes and sex chromosomes was synchronous. Two patterns of macrochromosomal synapsis were observed. Whereas synapsis of the biarmed elements was biterminal (i.e., progressing from both ends of the homologs), synapsis of the acrocentric elements was uniterminal involving only the distal (noncentromeric) ends of the homologs. Unique sex-chromosomal characteristics were not observed in S. grammicus and, therefore, the substaging of pachynema was based on subjective criteria. Examination of diakinesis – metaphase I and metaphase II configurations indicated low levels of diakinetic irregularities with balanced segregation of the autosomal bivalents and the sex-chromosomal trivalent.Key words: Sceloporus grammicus, meiosis, synaptonemal complex, substaging.