Delayed postglacial colonization of in Iceland and the circum North Atlantic.

As the Arctic continues to warm, woody shrubs are expected to expand northward. This process, known as 'shrubification,' has important implications for regional biodiversity, food web structure, and high-latitude temperature amplification. While the future rate of shrubification remains poorly constrained, past records of plant immigration to newly deglaciated landscapes in the Arctic may serve as useful analogs.

Microscopical palynology: Birch woodland expansion and species hybridisation coincide with periods of climate warming during the Holocene epoch in Iceland.

Introgressive hybridisation between arctic dwarf birch (Betula nana) and European downy birch (B. pubescens) is relatively common in natural woodlands in Iceland. As dwarf birch is a diploid species and downy tree birch a tetraploid species, their hybrids are triploid.

Evolutionary diversification of satellite DNA sequences from Leymus (Poaceae: Triticeae).

The genus Leymus (lymegrass) comprises about 30 polyploid, perennial, temperate grass species in the tribe Triticeae (family Poaceae). Previous studies indicated a large diversity in the Leymus genome, and therefore, the aim of this study was to isolate new repetitive DNA sequences that can be used for differentiating Leymus species and elucidating their genomic relationships. A C0t-1 DNA plasmid library was generated from genomic DNA of American tetraploid species Leymus triticoides.

Morphological variation among Betula nana (diploid), B. pubescens (tetraploid) and their triploid hybrids in Iceland.

Background And Aims: Introgressive hybridization between two co-existing Betula species in Iceland, diploid dwarf birch B. nana and tetraploid downy birch B. pubescens, has been well documented.

Identifying the genome of wood barley Hordelymus europaeus (Poaceae: Triticeae).

Wood barley, Hordelymus europaeus, was compared with other Triticeae species by Southern and fluorescence in situ hybridisation using total genomic DNA and repetitive sequences as probes. On Southern blots, the total genomic probe from H. europaeus hybridised strongly to DNA of its own species and to Leymus and Psathyrostachys, indicating the presence of Ns genome in H.

Preparation of chromosomes from plant leaf meristems for karyotype analysis and in situ hybridization.

A reliable method for preparing metaphase chromosomes from plant leaf tissues is described. The chromosomes are suitable for karyotype analysis and gene mapping by fluorescence in situ hybridisation (FISH). The method is based on enzymatic digestion of young leaf tissues (shoot-tips) after which the resulting protoplasts are treated hypotonically before being dropped onto microscopic slides.

Large retrotransposon derivatives: abundant, conserved but nonautonomous retroelements of barley and related genomes.

Retroviruses and LTR retrotransposons comprise two long-terminal repeats (LTRs) bounding a central domain that encodes the products needed for reverse transcription, packaging, and integration into the genome. We describe a group of retrotransposons in 13 species and four genera of the grass tribe Triticeae, including barley, with long, approximately 4.4-kb LTRs formerly called Sukkula elements.

Isolation, characterization, and analysis of Leymus-specific DNA sequences.

Genomic Southern hybridization using labeled total genomic DNA of Leymus mollis as probe showed intense hybridization signals on all restriction enzyme digested DNA from five species of Leymus Hochst., and four species of Psathyrostachys Nevski. Experiments using the same L.

The genome composition of hexaploid Psammopyrum athericum and octoploid Psammopyrum pungens (Poaceae: Triticeae).

The genomic constitution of two species in the genus Psammopyrum, i.e., Ps.

Genetic and genomic relationships in Leymus Hochst.

Genetic and genomic relationships among three taxonomically related species of Leymus, northern European L. arenarius (octoploid, 2n = 56), northern American/Pacific L. mollis (tetraploid, 2n = 28) and central Eurasian L.

Morphological, cytogenetic, and molecular evidence for introgressive hybridization in birch.

Extensive morphological variation of tetraploid birch (Betula pubescens) in Iceland is believed to be due to gene flow from diploid dwarf birch (B. nana) by means of introgressive hybridization. A combined morphological and cytogenetic approach was used to investigate this phenomenon in two geographically separated populations of natural birch woodland in Iceland.

Molecular cytogenetics of introgressive hybridization in plants.

Introgressive hybridization (introgression) is genetic modification of one species by another through hybridization and repeated backcrossing. Introgression is important in the evolution of flowering plants. It is also important in plant breeding where a desirable trait can be transferred from wild to crop species.

Genome discrimination by in situ hybridization in Icelandic species of Elymus and Elytrigia (Poaceae: Triticeae).

The genome constitution of Icelandic Elymus caninus, E. alaskanus, and Elytrigia repens was examined by fluorescence in situ hybridization using genomic DNA and selected cloned sequences as probes. Genomic in situ hybridization (GISH) of Hordeum brachyantherum ssp.

Trigenomic origin of the hexaploid Psammopyrum athericum (Triticeae: Poaceae) revealed by in-situ hybridization.

The genomic constitution of the hexaploid Psammopyrum athericum was studied with in-situ DNA hybridization using both genomic DNA and isolated cloned sequences as probes. A genomic probe from Thinopyrum bessarabicum (E genome) hybridized successfully to 14 chromosomes of Ps. athericum and a probe from Festucopsis serpentinii (L genome) hybridized to another 14 chromosomes.

Genomic and genetic relationships among species of Leymus (Poaceae: Triticeae) inferred from 18S-26S ribosomal genes.

The 18S-26S ribosomal genes in three closely related species of Leymus (Poaceae: Triticeae) were examined using fluorescence in situ hybridization (FISH) and restriction fragment length polymorphism (RFLP). Both approaches revealed a close relationship between L. arenarius (8x = 56, northern European) and L.

p53 abnormality and chromosomal instability in the same breast tumor cells.

To clarify the important role of the tumor-suppressor gene p53 in maintaining genetic integrity, we estimated chromosome instability and staining of overexpressed p53 protein in the same cells of five primary breast carcinomas. The method included both fluorescence immunohistochemistry and fluorescence in situ hybridization (FISH) on sections from formalin-fixed, paraffin-embedded breast cancer tissue. By using a centromeric FISH probe for chromosome 17 on interphase cells in these sections, we showed that cells with abnormal p53 protein expression had a statistically significant higher number of chromosome 17 than did cells with no p53 protein staining in the same samples as well as cells in four other tumor samples with no p53 protein staining.

Structure, functionality, and evolution of the BARE-1 retrotransposon of barley.

The BARE-1 retrotransposon is a major, active component of the genome of barley (Hordeum vulgare L.) and other Hordeum species. Copia-like in its organization, it consists of 1.

Retrotransposon BARE-1 and Its Role in Genome Evolution in the Genus Hordeum.

The replicative retrotransposon life cycle offers the potential for explosive increases in copy number and consequent inflation of genome size. The BARE-1 retrotransposon family of barley is conserved, disperse, and transcriptionally active. To assess the role of BARE-1 in genome evolution, we determined the copy number of its integrase, its reverse transcriptase, and its long terminal repeat (LTR) domains throughout the genus Hordeum.

Molecular variation in Leymus species and populations.

Icelandic populations of European lymegrass [Leymus arenarius (L.) Hochst.] were examined using amplified fragment length polymorphism (AFLP) and restriction fragment length polymorphism (RFLP) of the major ribosomal genes (18S-5.

Meiosis of wheat x lymegrass hybrids.

Meiosis was examined in pollen mother cells of F1 hybrids made from crosses between wheat (Triticum aestivum) and lymegrass (Leymus arenarius and L. mollis). Fluorescence genomic in situ hybridization detected pairing between wheat and lymegrass chromosomes during prophase I and metaphase I.

BRCA2 and p53 mutations in primary breast cancer in relation to genetic instability.

The products of the BRCA breast cancer susceptibility genes have been implicated in cell cycle control and DNA repair. It has been suggested that mutations in the p53 gene are a necessary step in tumorigenesis in BRCA tumors. We tested samples from 402 breast cancer patients for germ-line BRCA2 and p53 mutations in tumors.

Molecular genetics and cytogenetics of breast carcinomas: comparison of the two methods.

Molecular genetics and cytogenetics are two different approaches to studying genetic changes in breast carcinoma. We have used karyotype analysis, fluorescence in situ hybridization, and molecular analysis of allelic imbalance on chromosomes 7q and 16q and on both arms of chromosome 17, to study 85 breast carcinomas. Twenty-five of these samples gave results that could be used to compare the two methods.

Instability of chromosomes 1, 3, 16, and 17 in primary breast carcinomas inferred by fluorescence in situ hybridization.

Abnormalities of chromosomes 1, 3, 16, and 17 were examined in 203 metaphase cells from 12 cases of primary breast carcinoma using fluorescence in situ hybridization with chromosome painting probes. The most common structural abnormalities were chromosomal rearrangements, especially translocations, and chromosome 17 was most frequently involved in these types of changes. Chromosome 16 was preferentially involved in the losses and deletions, while chromosomes 1 and 17 were more involved in the gains, including amplifications, than other chromosomes.

Retrotransposon BARE-1 is a major, dispersed component of the barley (Hordeum vulgare L.) genome.

The barley BARE-1 is a transcribed, copia-like retroelement with well-conserved functional domains, an active promoter, and a copy number of at least 3 x 10(4). We examined its chromosomal localization by in situ hybridization. The long terminal repeat (LTR) probe displayed a uniform hybridization pattern over the whole of all chromosomes, excepting paracentromeric regions, telomeres, and nucleolar organizer (NOR) regions.