Inheritance of rDNA spacer length variants in man

1984 ◽  
Vol 196 (1) ◽  
pp. 141-145 ◽  
Author(s):  
Guglielmina N. Ranzani ◽  
Luigi F. Bernini ◽  
Marco Crippa
Keyword(s):  
Spacer Length ◽  
Spacer Length Variants

Molecular cloning and characterization of an unusually large intergenic spacer from the Nor-B2 locus of hexaploid wheat

Genome ◽  
1996 ◽  
Vol 39 (2) ◽  
pp. 288-292 ◽  
Author(s):  
R. K. Sardana ◽  
R. B. Flavell
Keyword(s):  
Key Words ◽  
Ribosomal Dna ◽  
Hexaploid Wheat ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Intergenic Spacer ◽  
Nucleolar Organizer ◽  
Spacer Length ◽  
Spacer Length Variants

An allelic rDNA variant from the Nor-B2 locus of 'Bezostaya' wheat that forms an especially active nucleolus was cloned and characterized. It carries an unusually large intergenic spacer compared with rDNA units in most other wheat genotypes. The additional intergenic length is in the array of 135-bp A repeats and not in other internal repeats. These A repeats have sequences nearly identical to other A repeats described for other alleles. It is suggested therefore that the more active Nor-B2 locus of 'Bezostaya' may be due to the constituent rDNA units possessing a larger array of A repeats. Key words : ribosomal DNA, nucleolar organizer region, A and B repeats, allelic, spacer length variants.

COMPARATIVE ASSESSMENT OF GENETIC DIVERSITY IN WILD AND CULTIVATED BARLEY USING RIBOSOMAL DNA SPACER LENGTH VARIANTS

1994 ◽  
Vol 42 (2) ◽  
pp. 115-123 ◽  
Author(s):  
Jeyanthi Ramamoorthy ◽  
Daniel K. Chong ◽  
C.C. Chinnappa
Keyword(s):  
Genetic Diversity ◽  
Ribosomal Dna ◽  
Mediterranean Region ◽  
Eastern Mediterranean ◽  
Eastern Mediterranean Region ◽  
Hordeum Spontaneum ◽  
Spacer Length ◽  
Frequency Distributions ◽  
Cultivated Barley ◽  
Spacer Length Variants

Ribosomal DNA spacer length variants (slv) were used to compare the genetic diversity between Hordeum spontaneum, the supposed progenitor of cultivated barley, and landraces of barley, H. vulgare, collected from three countries in the eastern Mediterranean region. A total of six rDNA slv and six slv phenotypes were observed. All six slv and phenotypes were found in both species. Nei's heterozygosity index was higher for landraces in all three countries. Landraces possessed slightly higher diversity than H. spontaneum. Slv phenotype 1 (112, 104) was the most predominant type in both species, and the frequency distributions for the two species were similar. This suggests that H. vulgare and H. spontaneum belong to the same polymorphic species. Furthermore, H. spontaneum seen today in the eastern Mediterranean region might have been derived from an extinct two-rowed ancestor.

The ribosomal DNA of Luzula pilosa (L.) Willd, a plant with holocentric chromosomes

Genome ◽  
1988 ◽  
Vol 30 (6) ◽  
pp. 915-923 ◽  
Author(s):  
B. A. Bowen ◽  
D. Lee ◽  
G. P. Creissen ◽  
G. E. Marks ◽  
C. A. Cullis
Keyword(s):  
Gene Conversion ◽  
Ribosomal Dna ◽  
Chromosome Breakage ◽  
Restriction Mapping ◽  
Haploid Genome ◽  
Holocentric Chromosomes ◽  
Spacer Length ◽  
Centromeric Dna ◽  
Entire Chromosome ◽  
Spacer Length Variants

The ribosomal DNA (rDNA) of Luzula pilosa (L.) Willd, a plant with holocentric chromosomes, has been cloned and characterized by restriction mapping. The major variant is present in about 730 tandemly arranged copies per haploid genome which occupy nearly an entire chromosome. We propose that much of the rDNA is flanked or interspersed by kinetochores, so that reciprocal interchromatid exchanges in this region would lead to chromosome breakage. Homogenization and amplification of rDNA spacer length variants may occur largely by intrachromatid exchanges and gene conversion. By trying to isolate rDNA junction fragments which might be closely linked to centromeric DNA, we have isolated three minor rDNA variants whose spacer regions do not cross-hybridize with one another or with the major variant. The possibility that these minor variants may be rRNA pseudogenes is discussed.Key words: centromere, holocentric, Luzula, rDNA, recombination.

Intergenic spacer length variants in Old Portuguese bread wheat cultivars

2011 ◽  
Vol 90 (2) ◽  
pp. 203-208 ◽  
Author(s):  
ANA CARVALHO ◽  
HENRIQUE GUEDES-PINTO ◽  
JOSÉ LIMA-BRITO
Keyword(s):  
Bread Wheat ◽  
Intergenic Spacer ◽  
Wheat Cultivars ◽  
Spacer Length ◽  
Old Portuguese ◽  
Spacer Length Variants

Variation of the intergenic spacer region of ribosomal DNA in cultivated and wild rice species

Genome ◽  
1990 ◽  
Vol 33 (2) ◽  
pp. 209-218 ◽  
Author(s):  
Y. Sano ◽  
R. Sano
Keyword(s):  
Ribosomal Dna ◽  
Intergenic Spacer ◽  
Length Variation ◽  
Cultivated Rice ◽  
Spacer Length ◽  
Intergenic Spacer Region ◽  
Wild Rice Species ◽  
Cultivated Species ◽  
Restriction Enzyme Maps ◽  
Spacer Length Variants

Spacer-length variation in ribosomal DNA (rDNA) was surveyed in two cultivated rice species and their wild relatives. Among 243 accessions observed, 18 different spacer-length variants were detected. Length heterogeneity was found within and among species as well as within individuals. Conventional genetic analysis revealed that two spacer-length variants were located at two unlinked loci. Restriction enzyme maps showed that length heterogeneity resulted from repetition of short repeated sequences in the intergenic spacer region in the Asian cultivar and its progenitor; however, the spacer region greatly differed from those of reproductively isolated taxa with respect to the length and the sequence. Furthermore, the Asian cultivated species and its progenitor were highly polymorphic for rDNA spacer-length variation and they were differentiated in frequencies of spacer-length variants as well as varietal groups within the cultivated species. Asian cultivars tended to carry homogeneous repeats of rDNA compared with their progenitor, suggesting different forms of homogenization occurring in Asian cultivars.Key words: ribosomal DNA, intergenic spacer, polymorphism, inheritance, Oryza.

Ribosomal DNA variations in wild and cultivated rubber tree (Hevea brasiliensis)

Genome ◽  
1993 ◽  
Vol 36 (6) ◽  
pp. 1049-1057 ◽  
Author(s):  
Pascale Besse ◽  
Marc Seguin ◽  
Patricia Lebrun ◽  
Claire Lanaud
Keyword(s):  
Ribosomal Dna ◽  
Hevea Brasiliensis ◽  
Geographical Origin ◽  
Rubber Tree ◽  
Intergenic Spacer ◽  
Type I ◽  
Spacer Length ◽  
High Level ◽  
Dna Variations ◽  
Spacer Length Variants

Ribosomal DNA variations were surveyed to assess the genetic variability among Hevea brasiliensis genetic resources. One hundred and sixty-eight individuals, including 73 cultivated Wickham clones and 95 wild clones from a prospection, were analyzed. Restriction mapping of rDNA units showed that RFLP variations are the result of both length and site (EcoRI) variations in the intergenic spacer (IGS). These variations can be revealed between as well as within individuals. A total of 12 spacer length variants is scored in the whole population, as well as two different ribosomal units (refered as type I and type II), defined by the presence or absence of an EcoRI site. Particular associations between spacer length variants and unit types can be revealed, leading to complex RFLP patterns. Cultivated clones appear to be less variable than prospections but show, however, a relatively high level of variability despite their narrow genetic base. Furthermore, IGS variations allowed a structuring within wild clones to be drawn, based mainly on their geographical origin. Some interesting discrepancies with previous work on isozyme variations are discussed and show the interest of surveying different genetic markers for diversity studies.Key words: Hevea brasiliensis, RFLP, rDNA, genetic diversity.

Structure-directing study of 1-methylimidazolium-based dication with tetramethylene as spacer length in the synthesis of microporous silicoaluminophosphates

2021 ◽  
Author(s):  
Thayara Kellen Tavares ◽  
Gabrielli Almeida ◽  
Yuri Variani ◽  
Katia Bernardo-Gusmão ◽  
Paloma Vinaches ◽  
...  
Keyword(s):  
Structure Directing Agent ◽  
Spacer Length ◽  
Organic Structure ◽  
Directing Effect

In this work we study the structure-directing effect of 1-methylimidazolium-based dications with four methylene units as spacer length (4BI), as Organic Structure-Directing Agent (OSDA) in the synthesis of silicoaluminophosphate (SAPO)...

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