Molecular characterization of ribosomal gene variation within and among NORs segregating in specialized populations of chicken

Genome ◽  
1999 ◽  
Vol 42 (1) ◽  
pp. 60-71 ◽  
Author(s):  
Mary E Delany ◽  
Alex B Krupkin
Keyword(s):  
Copy Number ◽  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Ribosomal Gene ◽  
Nucleolus Organizer ◽  
Molecular Organization ◽  
Gene Copy ◽  
Coding Region ◽  
Repeat Size ◽  
Red Jungle Fowl

The molecular organization of the 18S, 5.8S, and 28S ribosomal RNA gene repeat units, located at the single nucleolus organizer region (NOR) locus in the chicken, was investigated in genetically distinct populations of research and commercial chickens. Substantial gene repeat variation within and among NORs was documented. Intact ribosomal gene repeat size ranged from 11 kb to over 50 kb. Unique combinations of ribosomal genes, of different size, were specific to particular populations. It was determined that the basis for the ribosomal gene repeat size variation was intergenic spacer (IGS) length heterogeneity. Interestingly, in different populations, the location of the variation that contributes to length heterogeneity was specific to particular IGS subregions. In addition to IGS variation, an inbred line of Red Jungle Fowl exhibited coding region variation. Ribosomal gene copy number variation was also studied, and line averages ranged from 279 to 368. Average rDNA array size (a function of copy number and gene repeat length) was calculated for each of the populations and found to vary over a range of two megabases, from 5 to 7 Mb.Key words: rDNA, NOR, IGS, genetic variation, chicken.

scholarly journals Unbiased K-mer Analysis Reveals Changes in Copy Number of Highly Repetitive Sequences During Maize Domestication and Improvement

2016 ◽  
Author(s):  
Sanzhen Liu ◽  
Jun Zheng ◽  
Pierre Migeon ◽  
Jie Ren ◽  
Ying Hu ◽  
...  
Keyword(s):  
Copy Number ◽  
Organizer Region ◽  
Repetitive Sequences ◽  
Nucleolus Organizer Region ◽  
Nucleolus Organizer ◽  
45S Rdna ◽  
Specific Expression ◽  
Rdna Sequences ◽  
Rdna Expression ◽  
Maize Domestication

AbstractThe major component of complex genomes is repetitive elements, which remain recalcitrant to characterization. Using maize as a model system, we analyzed whole genome shotgun (WGS) sequences for the two maize inbred lines B73 and Mo17 using k-mer analysis to quantify the differences between the two genomes. Significant differences were identified in highly repetitive sequences, including centromere repeats, 45S ribosomal DNA (rDNA), knob, and telomere repeats. Previously unknown genotype specific 45S rDNA sequences were discovered. The B73-specific 45S rDNA is not only located on the nucleolus organizer region (NOR) on chromosome 6 but also dispersed on all the chromosomes in B73, indicating the relatively recent spread of 45S rDNA from the NOR. The B73 and Mo17 polymorphic k-mers were used to examine allele-specific expression of 45S rDNA. Although Mo17 contains higher copy number than B73, equivalent levels of overall 45S rDNA expression indicates that dosage compensation operates for the 45S rDNA in the hybrids. Using WGS sequences of B73xMo17 double haploids (DHs), genomic locations showing differential repetitive contents were genetically mapped. Analysis of WGS sequences of HapMap2 lines, including maize wild progenitor teosintes, landraces, and improved lines, decreases and increases in abundance of additional sets of k-mers associated with centromere repeats, 45S rDNA, knob, and retrotransposon sequences were found between teosinte and maize lines, revealing global evolutionary trends of genomic repeats during maize domestication and improvement.

scholarly journals THE NUCLEOLUS ORGANIZER REGION OF MAIZE (ZEA MAYS L.): TESTS FOR RIBOSOMAL GENE COMPENSATION OR MAGNIFICATION

Genetics ◽  
1974 ◽  
Vol 77 (2) ◽  
pp. 285-297
Author(s):  
R L Phillips ◽  
D F Weber ◽  
R A Kleese ◽  
S S Wang
Keyword(s):  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Ribosomal Gene ◽  
Nucleolus Organizer ◽  
Chromosome 6 ◽  
Gene Number ◽  
Normal Number ◽  
Whole Plant ◽  
Gene Compensation ◽  
Maize Plants

ABSTRACT Ribosomal gene compensation and magnification that might be detected on a whole-plant basis was not found in maize. Plants monosomic for chromosome 6 (the NOR chromosome) were compared with monosomic-8 and monosomic-10 plants, disomic sibs, and parental lines. Assuming no rDNA compensation, monosomic-6 plants showed approximately the decrease expected in rRNA cistron number. Monosomic-8 had a normal ribosomal gene number, while monosomic-10 showed a decrease; but further documentation is needed. Besides demonstrating the absence of gene compensation, the results document our previous conclusion that maize chromosome 6 carries DNA complementary to ribosomal RNA. Further documentation was provided from studies with trisomic chromosome 6 plants showing proportional increases in ribosomal gene number. Progeny of the monosomic plants crossed as males to a standard singlecross hybrid possessed expected ribosomal gene numbers suggesting the lack of ribosomal gene magnification.—The ragged (rgd) mutant of maize, suspected of being deficient in rRNA cistrons, had a normal number.

scholarly journals Genetic and molecular organization of ribosomal DNA (rDNA) variants in wild and cultivated barley.

Genetics ◽  
1990 ◽  
Vol 126 (3) ◽  
pp. 743-751
Author(s):  
R W Allard ◽  
M A Saghai Maroof ◽  
Q Zhang ◽  
R A Jorgensen
Keyword(s):  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Nucleolus Organizer ◽  
The Other ◽  
Molecular Organization ◽  
Genotypic Frequency ◽  
Spacer Length ◽  
Frequency Distributions ◽  
Cultivated Barley ◽  
The Individual

Abstract Twenty rDNA spacer-length variants (slvs) have been identified in barley. These slvs form a ladder in which each variant (with one exception) differs from its immediate neighbors by a 115-bp subrepeat. The 20 slvs are organized in two families, one forming an eight-step ladder (slvs 100-107) in the nucleolus organizer region (NOR) of chromosome 7 and the other a 12-step ladder (slvs 108a-118) in the NOR of chromosome 6. The eight shorter slvs (100-107) segregate and serve as markers of eight alleles of Mendelian locus Rrn2 and the 12 longer slvs (108a-118) segregate and serve as markers of 12 alleles of Mendelian locus Rrn1. Most barley plants (90%) are homozygous for two alleles, including one from each the 100-107 and the 108a-118 series. Two types of departures from this typical pattern of molecular and genetic organization were identified, one featuring compound alleles marked by two slvs of Rrn1 or of Rrn2, and the other featuring presence in Rrn1 of alleles normally found in Rrn2, and vice versa. The individual and joint effects on adaptedness of the rDNA alleles are discussed. It was concluded that selection acting on specific genotypes plays a major role in molding the strikingly different allelic and genotypic frequency distributions seen in populations of wild and cultivated barley from different ecogeographical regions.

Mapping of the nucleolus organizer region on chromosome 4 inArabidopsis thaliana

1996 ◽  
Vol 250 (1) ◽  
pp. 123-128
Author(s):  
Georg Haberer ◽  
Thilo C. Fischer ◽  
Ramón A. Torres-Ruiz
Keyword(s):  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Nucleolus Organizer ◽  
Chromosome 4

Hybrid ape offspring of a mating of gibbon and siamang

Science ◽  
1979 ◽  
Vol 205 (4403) ◽  
pp. 308-310 ◽  
Author(s):  
RH Myers ◽  
DA Shafer
Keyword(s):  
Parental Species ◽  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Structural Rearrangement ◽  
Female Offspring ◽  
Nucleolus Organizer ◽  
Single Chromosome ◽  
Symphalangus Syndactylus ◽  
Hylobates Moloch ◽  
Lesser Apes

The serendipitous mating of a male gibbon, Hylobates moloch, and a female siamang, Symphalangus syndactylus, has produced two female offspring born 1 year apart. The hybrid karyotype of 47 chromosomes comprises the haploid complements of the parental species, 22 for the gibbon and 25 for the siamang. Chromosomal G and C banding comparisons revealed no clear homologies between the parental karyotypes except for the single chromosome in each species containing the nucleolus organizer region. The lack of homology suggests that the structural rearrangement of chromosomes has played a major role in the process of speciation for these lesser apes.

scholarly journals The relationship between position and expression of genes on the kangaroo X chromosome suggests a tissue-specific spread of inactivation from a single control site

1988 ◽  
Vol 51 (2) ◽  
pp. 103-109 ◽  
Author(s):  
Jennifer A. Marshall Graves ◽  
Garey W. Dawson
Keyword(s):  
Alternative Hypothesis ◽  
Organizer Region ◽  
Nucleolus Organizer Region ◽  
Control Site ◽  
Specific Pattern ◽  
Nucleolus Organizer ◽  
Tissue Specific ◽  
Expression Of Genes ◽  
Control Locus ◽  
The Relationship

SummaryIn marsupials, X chromosome inactivation is paternal and incomplete. The tissue-specific pattern of inactivation of X-linked loci (G6PD, PGK, GLA) has been attributed to a piecemeal inactivation of different regions of the X. We here propose an alternative hypothesis, in which inactivation of the marsupial X is a chromosome-wide event, but is differentially regulated in different tissues. This hypothesis was suggested by the relationship between the positions and activity of genes on the kangaroo paternal X. In the absence of an HPRT polymorphism, we have used somatic cell hybridization to assess the activity of the paternal HPRT allele in lymphocytes and fibroblasts. The absence of the paternal X, and of the paternal forms of G6PD or PGK, from 33 cell hybrids made by fusing HPRT-deficient rodent cells with lymphocytes or fibroblasts of heterozygous females, suggests that the HPRT gene on the paternal X is inactive in both tissues and therefore not selectable. Since HPRT is located medially on the Xq near GLA, which shares the same characteristics of activity, we suggest that the locus-specific and tissue-specific patterns of activity result from a differential spread of inactivation from a single control locus, located near HPRT and GLA, outwards in both directions to G6PD and PGK. The nucleolus organizer region on the short arm does not seem to be part of the inactivated unit.

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