Nucleoli and ribosomal RNA cistron numbers in Hordeum species and interspecific hybrids exhibiting suppression of secondary constriction

Chromosoma ◽  
1978 ◽  
Vol 69 (2) ◽  
pp. 265-273 ◽  
Author(s):  
N. C. Subrahmanyam ◽  
A. A. Azad
Keyword(s):  
Ribosomal Rna ◽  
Interspecific Hybrids ◽  
Secondary Constriction ◽  
Hordeum Species

STUDIES ON THE RIBOSOMAL RNA CISTRONS IN INTERSPECIFIC DROSOPHILA HYBRIDS. II. HETEROCHROMATIC REGIONS MEDIATING NUCLEOLAR DOMINANCE

Genetics ◽  
1978 ◽  
Vol 89 (1) ◽  
pp. 37-64
Author(s):  
D S Durica ◽  
H M Krider
Keyword(s):  
Y Chromosome ◽  
Ribosomal Rna ◽  
Sex Chromosomes ◽  
Interspecific Hybrids ◽  
Secondary Constriction ◽  
Sex Chromosome ◽  
Heterochromatic Region ◽  
Nucleolus Organizer ◽  
F1 Hybrids ◽  
Nucleolar Dominance

ABSTRACT Interspecific hybrids of D. melanogaster and D. simulans normally exhibit a secondary constriction only at the D. melanogaster nucleolus organizer (NO). This phenomenon, termed nucleolar dominance, occurs only when the NO-bearing sex chromosomes of both species are present in conjunction. Experiments were initiated to localize regions on the sex chromosomes of D. melanogaster involved in mediating this suppression. Sex chromosome heterochromatic rearrangements and deficiencies were introduced into F1 hybrids and their corresponding effect on simulans NO constriction formation was examined in hybrid mitotic neuroblast tissue. Sex chromosomes deficient for both the D. melanogaster NO and adjacent heterochromatin were unable to restrict the formation of a constriction at the D. simulans NO. The presence of a D. melanogaster NO, however, was not sufficient for the establishment of nucleolar dominance. Results from an array of NO-bearing X and Y chromosome rearrangements and deficiencies indicate that at least one heterochromatic region, proximal to the NO on the D. melanogaster X and distal to the NO on the D. melanogaster Y, affects the induction of this interchromosomal phenomenon.

scholarly journals Locations of 18S and 28S ribosomal genes on the chromosomes of the Indian muntjac.

1975 ◽  
Vol 64 (1) ◽  
pp. 251-254 ◽  
Author(s):  
M L Pardue ◽  
T C Hsu
Keyword(s):  
In Situ Hybridization ◽  
Ribosomal Rna ◽  
Secondary Constriction ◽  
Ribosomal Genes ◽  
Metaphase Chromosomes ◽  
Indian Muntjac ◽  
Secondary Constrictions

The locations of genes coding for 18S and 28S ribosomal RNA have been mapped on metaphase chromosomes of the Indian muntjac M. muntjak by in situ hybridization with (3H)rRNA from the toad X. laevis. The results show that, in the muntjac, rDNA clusters are associated with the prominent secondary constrictions on the X and the Y1 chromos. In addition a cluster of rDNA is found near the tip of one arm on the longest pair of autosomes. The autosomal cluster of rDNAs usually does not express as a secondary constriction at metaphase.

Meiosis in interspecific Hordeum hybrids. I. Diploid combinations

1986 ◽  
Vol 28 (4) ◽  
pp. 525-535 ◽  
Author(s):  
Roland Von Bothmer ◽  
Jan Flink ◽  
Thomas Landström
Keyword(s):  
Interspecific Hybrids ◽  
Genomic Structure ◽  
Genetic Regulation ◽  
The Other ◽  
South American ◽  
Meiotic Pairing ◽  
Hordeum Bulbosum ◽  
High Affinity ◽  
Hordeum Species ◽  
Pairing Behaviour

The meiotic pairing behaviour of 39 new interspecific combinations between diploid Hordeum species are reported. On the basis of this data, four "basic genomes" are probably present in the genus. Hordeum bulbosum and H. vulgare have the same genome (I); H. marinum ("X") and H. murinum ("Y") each have one distinct genome. All other diploid taxa have either the same or a somewhat modified form of genome H. In this latter group of diploids, the South American taxa together with H. pusillum and H. intercedens in North America constitue a homogeneous group with respect to genomic structure, which differs somewhat from that found in the other Asiatic and North American species. Hordeum roshevitzii from Central Asia is unique, showing high affinity to both the Asiatic and to the American taxa. Evidence suggesting genetic regulation of chromosome pairing (both pairing promoting and pairing reducing) was obtained from a number of the diploid hybrids.Key words: Hordeum, interspecific hybrids, meiosis, diploids.

Meiosis in interspecific Hordeum hybrids. IV. Tetraploid (4x × 4x) hybrids

Genome ◽  
1988 ◽  
Vol 30 (4) ◽  
pp. 479-485 ◽  
Author(s):  
Roland von Bothmer ◽  
Jan Flink ◽  
Tomas Landström
Keyword(s):  
Interspecific Hybrids ◽  
Genetic Regulation ◽  
The Other ◽  
Meiotic Pairing ◽  
Genomic Constitution ◽  
Hordeum Species ◽  
Hordeum Brevisubulatum ◽  
Pairing Behaviour

The meiotic pairing behaviour of 31 interspecific combinations of tetraploid Hordeum species are reported. The autoploid H. bulbosum with the II genomic constitution has no homology to the other species. The constitution of tetraploid H. murinum is not clear, but it is not homologous to other tetraploids. Hordeum marinum is a probable autoploid (XX) but with a very strong genetic regulation of pairing. The X genome is possibly found in H. secalinum and H. capense, both of which also possess the H genome in several diploids. Hordeum fuegianum, H. tetraploidum, H. jubatum, H. brachyantherum, and H. roshevitzii are segmental alloploids all with the same two partly homoeologous genomes. Hordeum depressum is probably a segmental alloploid with the H genome and with a very strong pairing regulation. Hordeum brevisubulatum is a pure autoploid with two homologous H genomes.Key words: Hordeum, interspecific hybrids, meiosis, tetraploids.

Genetic control of meiotic chromosome pairing in polyploids in the genus Hordeum

1985 ◽  
Vol 27 (5) ◽  
pp. 515-530 ◽  
Author(s):  
P. K. Gupta ◽  
George Fedak
Keyword(s):  
Chromosome Pairing ◽  
Interspecific Hybrids ◽  
Meiotic Chromosome ◽  
Intergeneric Hybrid ◽  
Meiotic Pairing ◽  
Major Locus ◽  
In The Wild ◽  
Hordeum Species ◽  
Homoeologous Chromosomes ◽  
Existing Data

Existing data on meiosis in hexaploid and tetraploid species of Hordeum, their respective polyhaploids, and intergeneric – interspecific hybrids indicate that a meiotic pairing control system exists in this genus. The system is probably polygenic and it is therefore unlikely that a major locus such as Ph in Triticum controls chromosome pairing. It is more efficient in the tetraploids than hexaploids, permitting some intergenomic pairing in the latter. In the polyhaploids the pairing control is somewhat hemizygous ineffective. The pairing of homoeologous chromosomes in the wild polyploid Hordeum species is generally inhibited by H. vulgare and variably enhanced by genomes of Secale species.Key words: Hordeum, synapsis regulation, intergeneric hybrid, polyhaploids, hemizygous.

Visualisation of E. coli ribosomal RNA in situ by electron spectroscopic imaging and image averaging

1992 ◽  
Vol 50 (1) ◽  
pp. 466-467
Author(s):  
Daniel Beniac ◽  
George Harauz
Keyword(s):  
Ribosomal Rna ◽  
Three Dimensional ◽  
Spectroscopic Imaging ◽  
Electron Spectroscopic Imaging ◽  
E Coli ◽  
Microscopical Technique ◽  
Quantitative Image ◽  
Dimensional Reconstruction ◽  
Image Averaging ◽  
Protein Components

The structures of E. coli ribosomes have been extensively probed by electron microscopy of negatively stained and frozen hydrated preparations. Coupled with quantitative image analysis and three dimensional reconstruction, such approaches are worthwhile in defining size, shape, and quaternary organisation. The important question of how the nucleic acid and protein components are arranged with respect to each other remains difficult to answer, however. A microscopical technique that has been proposed to answer this query is electron spectroscopic imaging (ESI), in which scattered electrons with energy losses characteristic of inner shell ionisations are used to form specific elemental maps. Here, we report the use of image sorting and averaging techniques to determine the extent to which a phosphorus map of isolated ribosomal subunits can define the ribosomal RNA (rRNA) distribution within them.

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