scholarly journals Hill–Robertson interference in Drosophila melanogaster: reply to Marais, Mouchiroud and Duret

2003 ◽  
Vol 81 (2) ◽  
pp. 89-90 ◽  
Author(s):  
RICHARD M. KLIMAN ◽  
JODY HEY
Keyword(s):  
Drosophila Melanogaster ◽  
Codon Usage ◽  
Recombination Rate ◽  
Base Composition ◽  
Potential Role ◽  
Compositional Bias ◽  
Stochastic Effects ◽  
Protein Coding ◽  
Biasing Effects ◽  
Preferred Codon

The usage of preferred codons in Drosophila melanogaster is reduced in regions of lower recombination. This is consistent with population genetics theory, whereby the effectiveness of selection on multiple targets is limited by stochastic effects caused by linkage. However, because the selectively preferred codons in D. melanogaster end in C or G, it has been argued that base-composition-biasing effects of recombination can account for the observed relationship between preferred codon usage and recombination rate (Marais et al., 2003). Here, we show that the correlation between base composition (of protein-coding and intron regions) and recombination rate holds only for lower values of the latter. This is consistent with a Hill–Robertson interference model and does not support a model whereby the entire effect of recombination on codon usage can be attributed to its potential role in generating compositional bias.

scholarly journals HeT-A, a transposable element specifically involved in "healing" broken chromosome ends in Drosophila melanogaster.

1992 ◽  
Vol 12 (9) ◽  
pp. 3910-3918 ◽  
Author(s):  
H Biessmann ◽  
K Valgeirsdottir ◽  
A Lofsky ◽  
C Chin ◽  
B Ginther ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Transposable Element ◽  
Sequence Homology ◽  
Base Composition ◽  
Short Range ◽  
Pericentric Heterochromatin ◽  
Open Reading Frames ◽  
Protein Coding ◽  
Reading Frames ◽  
Range Variation

Eight terminally deleted Drosophila melanogaster chromosomes have now been found to be "healed." In each case, the healed chromosome end had acquired sequence from the HeT DNA family, a complex family of repeated sequences found only in telomeric and pericentric heterochromatin. The sequences were apparently added by transposition events involving no sequence homology. We now report that the sequences transposed in healing these chromosomes identify a novel transposable element, HeT-A, which makes up a subset of the HeT DNA family. Addition of HeT-A elements to broken chromosome ends appears to be polar. The proximal junction between each element and the broken chromosome end is an oligo(A) tract beginning 54 nucleotides downstream from a conserved AATAAA sequence on the strand running 5' to 3' from the chromosome end. The distal (telomeric) ends of HeT-A elements are variably truncated; however, we have not yet been able to determine the extreme distal sequence of a complete element. Our analysis covers approximately 2,600 nucleotides of the HeT-A element, beginning with the oligo(A) tract at one end. Sequence homology is strong (greater than 75% between all elements studied). Sequence may be conserved for DNA structure rather than for protein coding; even the most recently transposed HeT-A elements lack significant open reading frames in the region studied. Instead, the elements exhibit conserved short-range sequence repeats and periodic long-range variation in base composition. These conserved features suggest that HeT-A elements, although transposable elements, may have a structural role in telomere organization or maintenance.

scholarly journals Contrasting patterns of sequence divergence and base composition between Drosophila introns and intergenic regions

2006 ◽  
Vol 2 (4) ◽  
pp. 604-607 ◽  
Author(s):  
Lino Ometto ◽  
David De Lorenzo ◽  
Wolfgang Stephan
Keyword(s):  
Drosophila Melanogaster ◽  
Recombination Rate ◽  
Base Composition ◽  
Gc Content ◽  
Sequence Divergence ◽  
Evolutionary Patterns ◽  
Nucleotide Variability ◽  
Selective Constraints ◽  
Intergenic Regions

Two non-coding DNA classes, introns and intergenic regions, of Drosophila melanogaster exhibit contrasting evolutionary patterns. GC content is significantly higher in intergenic regions and affects their degree of nucleotide variability. Divergence is positively correlated with recombination rate in intergenic regions, but not in introns. We argue that these differences are due to different selective constraints rather than mutational or recombinational mechanisms.

HeT-A, a transposable element specifically involved in "healing" broken chromosome ends in Drosophila melanogaster

1992 ◽  
Vol 12 (9) ◽  
pp. 3910-3918
Author(s):  
H Biessmann ◽  
K Valgeirsdottir ◽  
A Lofsky ◽  
C Chin ◽  
B Ginther ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Transposable Element ◽  
Sequence Homology ◽  
Base Composition ◽  
Short Range ◽  
Pericentric Heterochromatin ◽  
Open Reading Frames ◽  
Protein Coding ◽  
Reading Frames ◽  
Range Variation

Eight terminally deleted Drosophila melanogaster chromosomes have now been found to be "healed." In each case, the healed chromosome end had acquired sequence from the HeT DNA family, a complex family of repeated sequences found only in telomeric and pericentric heterochromatin. The sequences were apparently added by transposition events involving no sequence homology. We now report that the sequences transposed in healing these chromosomes identify a novel transposable element, HeT-A, which makes up a subset of the HeT DNA family. Addition of HeT-A elements to broken chromosome ends appears to be polar. The proximal junction between each element and the broken chromosome end is an oligo(A) tract beginning 54 nucleotides downstream from a conserved AATAAA sequence on the strand running 5' to 3' from the chromosome end. The distal (telomeric) ends of HeT-A elements are variably truncated; however, we have not yet been able to determine the extreme distal sequence of a complete element. Our analysis covers approximately 2,600 nucleotides of the HeT-A element, beginning with the oligo(A) tract at one end. Sequence homology is strong (greater than 75% between all elements studied). Sequence may be conserved for DNA structure rather than for protein coding; even the most recently transposed HeT-A elements lack significant open reading frames in the region studied. Instead, the elements exhibit conserved short-range sequence repeats and periodic long-range variation in base composition. These conserved features suggest that HeT-A elements, although transposable elements, may have a structural role in telomere organization or maintenance.

scholarly journals Chromosomal Distribution of Transposable Elements in Drosophila melanogaster Test of the Ectopic Recombination Model for Maintenance of Insertion Site Number

Genetics ◽  
1996 ◽  
Vol 144 (1) ◽  
pp. 197-204
Author(s):  
Christine Hoogland ◽  
Christian Biémont
Keyword(s):  
Drosophila Melanogaster ◽  
Transposable Elements ◽  
Dna Content ◽  
Recombination Rate ◽  
Alternative Hypothesis ◽  
Insertion Site ◽  
Polytene Chromosomes ◽  
Negative Relationship ◽  
Site Occupancy ◽  
Site Number

Abstract Data of insertion site localization and site occupancy frequency of P, hobo, I, copia, mdg1, mdg3, 412, 297, and roo transposable elements (TEs) on the polytene chromosomes of Drosophila melanogaster were extracted from the literature. We show that TE insertion site number per chromosomal division was significantly correlated with the amount of DNA. The insertion site number weighted by DNA content was not correlated with recombination rate for all TEs except hobo, for which a positive correlation was detected. No global tendency emerged in the relationship between TE site occupancy frequency, weighted by DNA content, and recombination rate; a strong negative correlation was, however, found for the 3L arm. A possible dominant deleterious effect of chromosomal rearrangements due to recombination between TE insertions is thus not the main factor explaining the dynamics of TEs, since this hypothesis implies a negative relationship between recombination rate and both TE insertion site number and site occupancy frequency. The alternative hypothesis of selection against deleterious effects of insertional mutations is discussed.

scholarly journals Patterns of DNA Variability at X-Linked Loci in Mus domesticus

Genetics ◽  
1997 ◽  
Vol 147 (3) ◽  
pp. 1303-1316
Author(s):  
Michael W Nachman
Keyword(s):  
Drosophila Melanogaster ◽  
X Chromosome ◽  
House Mouse ◽  
Recombination Rate ◽  
Nucleotide Diversity ◽  
Mus Domesticus ◽  
Substantial Variation ◽  
Intraspecific Polymorphism ◽  
Recombination Rates ◽  
Interspecific Divergence

Introns of four X-linked genes (Hprt, Plp, Glra2, and Amg) were sequenced to provide an estimate of nucleotide diversity at nuclear genes within the house mouse and to test the neutral prediction that the ratio of intraspecific polymorphism to interspecific divergence is the same for different loci. Hprt and Plp lie in a region of the X chromosome that experiences relatively low recombination rates, while Glra2 and Amg lie near the telomere of the X chromosome, a region that experiences higher recombination rates. A total of 6022 bases were sequenced in each of 10 Mus domesticus and one M. caroli. Average nucleotide diversity (π) for introns within M. domesticus was quite low (π = 0.078%). However, there was substantial variation in the level of heterozygosity among loci. The two telomeric loci, Glra2 and Amg, had higher ratios of polymorphism to divergence than the two loci experiencing lower recombination rates. These results are consistent with the hypothesis that heterozygosity is reduced in regions with lower rates of recombination, although sampling of additional genes is needed to establish whether there is a general correlation between heterozygosity and recombination rate as in Drosophila melanogaster.

scholarly journals Consequences of Recombination Rate Variation on Quantitative Trait Locus Mapping Studies: Simulations Based on the Drosophila melanogaster Genome

Genetics ◽  
2001 ◽  
Vol 159 (2) ◽  
pp. 581-588
Author(s):  
Mohamed A F Noor ◽  
Aimee L Cunningham ◽  
John C Larkin
Keyword(s):  
Quantitative Trait Locus ◽  
Drosophila Melanogaster ◽  
Qtl Mapping ◽  
Quantitative Trait ◽  
Recombination Rate ◽  
Genome Project ◽  
Gene Density ◽  
Rate Variation ◽  
Trait Locus ◽  
Recombination Rate Variation

Abstract We examine the effect of variation in gene density per centimorgan on quantitative trait locus (QTL) mapping studies using data from the Drosophila melanogaster genome project and documented regional rates of recombination. There is tremendous variation in gene density per centimorgan across this genome, and we observe that this variation can cause systematic biases in QTL mapping studies. Specifically, in our simulated mapping experiments of 50 equal-effect QTL distributed randomly across the physical genome, very strong QTL are consistently detected near the centromeres of the two major autosomes, and few or no QTL are often detected on the X chromosome. This pattern persisted with varying heritability, marker density, QTL effect sizes, and transgressive segregation. Our results are consistent with empirical data collected from QTL mapping studies of this species and its close relatives, and they explain the “small X-effect” that has been documented in genetic studies of sexual isolation in the D. melanogaster group. Because of the biases resulting from recombination rate variation, results of QTL mapping studies should be taken as hypotheses to be tested by additional genetic methods, particularly in species for which detailed genetic and physical genome maps are not available.

The destabilizing elements in the coding region of c-fos mRNA are recognized as RNA

1993 ◽  
Vol 13 (8) ◽  
pp. 5034-5042
Author(s):  
C L Wellington ◽  
M E Greenberg ◽  
J G Belasco
Keyword(s):  
Codon Usage ◽  
Mammalian Cells ◽  
Mrna Decay ◽  
Polypeptide Chain ◽  
Coding Region ◽  
Protein Coding ◽  
Present Evidence ◽  
Reading Frame ◽  
Nascent Polypeptide

The protein-coding region of the c-fos proto-oncogene transcript contains elements that direct the rapid deadenylation and decay of this mRNA in mammalian cells. The function of these coding region instability determinants requires movement of ribosomes across mRNAs containing them. Three types of mechanisms could account for this translational requirement. Two of these possibilities, (i) that rapid mRNA decay might be mediated by the nascent polypeptide chain and (ii) that it might result from an unusual codon usage, have experimental precedent. Here, we present evidence that the destabilizing elements in the c-fos coding region are not recognized in either of these two ways. Instead, the ability of the c-fos coding region to function as a potent mRNA destabilizer when translated in the +1 reading frame indicates that the signals for rapid deadenylation and decay reside in the sequence or structure of the RNA comprising this c-fos domain.

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