scholarly journals Evolution of the Ribosomal DNA Spacers of Drosophila melanogaster: Different Patterns of Variation on X and Y Chromosomes

Genetics ◽  
1987 ◽  
Vol 116 (2) ◽  
pp. 225-232
Author(s):  
Scott M Williams ◽  
Glenn R Furnier ◽  
Eric Fuog ◽  
Curtis Strobeck
Keyword(s):  
Drosophila Melanogaster ◽  
Natural Selection ◽  
Ribosomal Dna ◽  
Genomic Dna ◽  
Restriction Enzymes ◽  
Ribosomal Gene ◽  
Length Variation ◽  
Spacer Length ◽  
Y Chromosomes ◽  
The World

ABSTRACT Length variation of the ribosomal gene spacers of Drosophila melanogaster was studied. Analysis of 47 X chromosomal and 47 Y chromosomal linked rDNA arrays collected from five continents indicates that the arrays on the two chromosomes differ qualitatively. The Y-linked arrays from around the world share little or no similarity for either their overall length or the organization of their spacers. Most of the X-linked arrays do, however, share a major length spacer of 5.1 kb. In addition, those X-linked arrays that have a major 5.1-kb band have similar spacer organization as demonstrated by genomic DNA digestions with several restriction enzymes. These data strongly support the hypothesis that spacer length patterns on only X-linked genes are maintained primarily by natural selection.

scholarly journals Reciprocal recombination and the evolution of the ribosomal gene family of Drosophila melanogaster.

Genetics ◽  
1989 ◽  
Vol 122 (3) ◽  
pp. 617-624 ◽  
Author(s):  
S M Williams ◽  
J A Kennison ◽  
L G Robbins ◽  
C Strobeck
Keyword(s):  
Drosophila Melanogaster ◽  
Gene Family ◽  
Ribosomal Rna ◽  
Natural Populations ◽  
Ribosomal Gene ◽  
Gene Region ◽  
Ribosomal Rna Gene ◽  
Reciprocal Recombination ◽  
Y Chromosomes ◽  
Length Polymorphisms

Abstract The role of reciprocal recombination in the coevolution of the ribosomal RNA gene family on the X and Y chromosomes of Drosophila melanogaster was assessed by determining the frequency and nature of such exchange. In order to detect exchange events within the ribosomal RNA gene family, both flanking markers and restriction fragment length polymorphisms within the tandemly repeated gene family were used. The vast majority of crossovers between flanking markers were within the ribosomal RNA gene region, indicating that this region is a hotspot for heterochromatic recombination. The frequency of crossovers within the ribosomal RNA gene region was approximately 10(-4) in both X/X and X/Y individuals. In conjunction with published X chromosome-specific and Y chromosome-specific sequences and restriction patterns, the data indicate that reciprocal recombination alone cannot be responsible for the observed variation in natural populations.

A comparative analysis of genetic polymorphism in wild and cultivated barley from Tibet using isozyme and ribosomal DNA markers

Genome ◽  
1994 ◽  
Vol 37 (4) ◽  
pp. 631-638 ◽  
Author(s):  
Qifa Zhang ◽  
G. P. Yang ◽  
Xiankai Dai ◽  
J. Z. Sun
Keyword(s):  
Genetic Variation ◽  
Ribosomal Dna ◽  
Wild Barley ◽  
Length Variation ◽  
Spacer Length ◽  
Origin And Evolution ◽  
Centre Of Diversity ◽  
Esterase Loci ◽  
Cultivated Barley ◽  
Comparison Of The Results

This study was conducted to address some of the issues concerning the possible significance of Tibet in the origin and evolution of cultivated barley. A total of 1757 barley accessions from Tibet, including 1496 entries of Hordeum vulgare ssp. vulgare (HV), 229 entries of the six-rowed wild barley H. vulgare ssp. agriocrithon (HA), and 32 entries of the two-rowed wild barley H. vulgare ssp. spontaneum (HS), were assayed for allozymes at four esterase loci. A subsample of 491 accessions was surveyed for spacer-length polymorphism at two ribosomal DNA loci. Genetic variation is extensive in these barley groups, and the amount of genetic diversity in cultivated barley of this region is comparable with that of cultivated barley worldwide. The level of genetic variation of HA is significantly lower than the other two barley groups, and there is also substantial heterogeneity in the level of polymorphism among different agrigeographical subregions. However, little genetic differentiation was detected among the three barley groups (HV, HA, and HS), as well as among different agrigeographical subregions. Comparison of the results from this and previous studies indicated a strong differentiation between Oriental and Occidental barley, thus favoring the hypothesis of a diphyletic origin of cultivated barley.Key words: Hordeum, allozyme, rDNA spacer-length variation, centre of diversity, phylogeny.

Temporal variation in the ribosomal DNA nontranscribed spacer of Aedes albopictus (Diptera: Culicidae)

Genome ◽  
1991 ◽  
Vol 34 (2) ◽  
pp. 293-297 ◽  
Author(s):  
Srinivas Kambhampati ◽  
Karamjit S. Rai
Keyword(s):  
Temporal Variation ◽  
Aedes Albopictus ◽  
Ribosomal Dna ◽  
Population Variation ◽  
High Rate ◽  
Length Variation ◽  
Spacer Length ◽  
Nontranscribed Spacer ◽  
Population Component ◽  
Different Populations

Length variation in ribosomal DNA (rDNA) nontranscribed spacer within and among populations of the mosquito Aedes albopictus was studied over a 3-year period in eight different populations from Texas. Statistically significant variation was detected among populations at each sampling date. Significant, but nondirectional, changes were observed within populations over time. An average of 78% of the total variance in the frequencies of spacer variants was attributable to the within-population component, suggesting local differentiation. The results corroborate those from a previous study on spacer length diversity in populations of A. albopictus from around the world and are similar to those from a study on temporal variation in allozyme frequencies in some of the same populations and sampling dates. We propose that a high rate of production of length variants and localized breeding structure could explain the observed high levels of within- and among-population variation in A. albopictus.Key words: rDNA, nontranscribed spacer, genetic structure, temporal variation, Aedes albopictus.

scholarly journals THE EFFECT OF ABO PHENOTYPIC EXPRESSION ON RIBOSOMAL DNA INSTABILITIES IN DROSOPHILA MELANOGASTER

Genetics ◽  
1979 ◽  
Vol 92 (3) ◽  
pp. 879-889
Author(s):  
Hallie M Krider ◽  
Barry Yedvobnick ◽  
Bryan I Levine
Keyword(s):  
Drosophila Melanogaster ◽  
Ribosomal Dna ◽  
Maternal Effect ◽  
Phenotypic Expression ◽  
Mutant Phenotype ◽  
Y Chromosomes ◽  
Homozygous Mutant ◽  
Successive Generations ◽  
Adult Drosophila

ABSTRACT The recessive maternal-effect mutation, abnormal oocyte (abo:2-38), reduces viability in the offspring of homozygous mutant females. Zygotes lacking specific heterochromatic segments of the X or Y chromosomes are most severely affected. We have shown that abo/abo lines can lose the capacity to express the mutant phenotype, and that elevated rDNA redundancies can be observed in such stocks (KRILIER and LEVINE 1975). In this study, we describe a microhybridization procedure that facilitates the measurement of rDNA redundancy, using a small number of adult Drosophila. We show that instability of the rDNA content persists in an abo/abo line after loss of the capacity to express the phenotype, and that changes in rDNA amounts occur between successive generations of the stock. Further, we show that the rDNA content of XO progeny from abo/abo females is elevated. The effect is directly correlated with the expression of the abo phenotype, and it is not observed in the XO progeny of abo heterozygous females or abo homozygotes from lines that do not show abo expression.

Ribosomal DNA spacer-length variation inSecale spp. (Poaceae)

1990 ◽  
Vol 171 (1-4) ◽  
pp. 205-220 ◽  
Author(s):  
P. Reddy ◽  
R. Appels ◽  
B. R. Baum
Keyword(s):  
Ribosomal Dna ◽  
Length Variation ◽  
Spacer Length

scholarly journals Intraspecific and interspecific variation at the y-ac-sc region of Drosophila simulans and Drosophila melanogaster.

Genetics ◽  
1992 ◽  
Vol 130 (4) ◽  
pp. 805-816 ◽  
Author(s):  
J M Martín-Campos ◽  
J M Comerón ◽  
N Miyashita ◽  
M Aguadé
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
Length Polymorphism ◽  
Restriction Site ◽  
Natural Populations ◽  
Restriction Enzymes ◽  
Drosophila Simulans ◽  
Population Subdivision ◽  
Telomeric Region ◽  
Length Variation

Abstract A 2.2-kb region including the ac gene of Drosophila simulans has been sequenced. Interspecific divergence between Drosophila melanogaster and D. simulans was estimated as 0.0695 and 0.0558 for silent and for all sites, respectively. Estimated silent site divergence for the ac region is comparable to that estimated for other regions of the genome between these species, indicating that silent sites of the ac region are not under significantly stronger functional constraint. Intraspecific variation in both species was also investigated. Restriction-site and length polymorphism in the ac region of D. simulans has been investigated for 103 X chromosome lines sampled from three natural populations in Spain using eight four-cutter restriction enzymes. Neither restriction-site nor length variation was detected in the three populations surveyed. In D. melanogaster restriction-site and length polymorphism in all major transcription units of the y-ac-sc region (23.1-kb region) has been studied using four four-cutter restriction enzymes for 245 X chromosome lines sampled from 10 natural populations (seven from Europe, two from North America and one from Japan). Fourteen restriction-site and 28 length polymorphisms were detected. There was some indication of population subdivision for North American vs. European samples of D. melanogaster. The frequency spectrum of restriction-site polymorphisms in European populations was skewed toward rarer frequencies than predicted by the neutral theory. Comparison of silent site variation at this telomeric region with that in the Adh 5'-flanking region showed a reduced level of heterozygosity in the y-ac-sc region. Since interspecific silent divergence is not reduced in the y-ac-sc region as compared to other regions, the reduction in standing levels of variation at this telomeric locus in both D. simulans and D. melanogaster is most easily explained by a hitchhiking effect of linked selected substitutions.

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.

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