Unequal crossing-over between yeast transposable elements

1983 ◽  
Vol 190 (1) ◽  
pp. 117-121 ◽  
Author(s):  
G. Shirleen Roeder
Keyword(s):  
Transposable Elements ◽  
Crossing Over ◽  
Unequal Crossing Over

scholarly journals Special Issue: Repetitive DNA Sequences

Genes ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 896
Author(s):  
Sarah E. Lower ◽  
Anne-Marie Dion-Côté ◽  
Andrew G. Clark ◽  
Daniel A. Barbash
Keyword(s):  
Transposable Elements ◽  
Genome Evolution ◽  
Dna Sequences ◽  
New Technologies ◽  
Crossing Over ◽  
Special Issue ◽  
Satellite Dnas ◽  
Replication Slippage ◽  
Repetitive Dnas ◽  
Unequal Crossing Over

Repetitive DNAs are ubiquitous in eukaryotic genomes and, in many species, comprise the bulk of the genome. Repeats include transposable elements that can self-mobilize and disperse around the genome and tandemly-repeated satellite DNAs that increase in copy number due to replication slippage and unequal crossing over. Despite their abundance, repetitive DNAs are often ignored in genomic studies due to technical challenges in identifying, assembling, and quantifying them. New technologies and methods are now allowing unprecedented power to analyze repetitive DNAs across diverse taxa. Repetitive DNAs are of particular interest because they can represent distinct modes of genome evolution. Some repetitive DNAs form essential genome structures, such as telomeres and centromeres, that are required for proper chromosome maintenance and segregation, while others form piRNA clusters that regulate transposable elements; thus, these elements are expected to evolve under purifying selection. In contrast, other repeats evolve selfishly and cause genetic conflicts with their host species that drive adaptive evolution of host defense systems. However, the majority of repeats likely accumulate in eukaryotes in the absence of selection due to mechanisms of transposition and unequal crossing over. However, even these “neutral” repeats may indirectly influence genome evolution as they reach high abundance. In this Special Issue, the contributing authors explore these questions from a range of perspectives.

Cloning and characterization of a transposable-like repeat in the heterochromatin of the darkling beetle Misolampus goudoti

Genome ◽  
2004 ◽  
Vol 47 (4) ◽  
pp. 769-774 ◽  
Author(s):  
Joan Pons
Keyword(s):  
Transposable Elements ◽  
Transposable Element ◽  
Satellite Dna ◽  
Molecular Mechanisms ◽  
Repeat Unit ◽  
Nucleotide Composition ◽  
Crossing Over ◽  
Unequal Crossing Over ◽  
Darkling Beetle

A long repeat unit of the PstI family in Misolampus goudoti (Coleoptera, Tenebrionodae) is characterized in this work. The 30 sequenced units have small differences in length (consensus 1169 bp), but very similar nucleotide composition (mean 61.1% A+T). PstI repeats contain a 36-bp-long inverted repeat at both the 5′ and 3′ ends, with a fully conserved 16-bp-long motif similar to those found in class II transposable elements. However, the transposable-like PstI repeats seems to be defective, since they do not encode for any protein related with transposition. Interestingly, energetically stable hairpins resembled the structure of a miniature interspersed transposable element, suggesting that the PstI satellite DNA family in M. goudoti may have originated from an ancestral active transposable element as also described in Drosophila guanche. The presence of transposable-like structure along with the non-detection of gene conversion or unequal crossing-over events suggest that transposition could be one of the putative molecular mechanisms involved in the strong amplification and (or) homogenization of these repeats. A putative transposition of PstI repeats allowing their genomic mobility also could explain why this satellite is widely distributed to all heterochromatic regions, telomeres, pericentromeric regions, and on the Y chromosome, whereas satellites of other tenebrionids lacking transposable-like structures are restricted only to pericentromeric regions.Key words: transposable elements, MITE, satellite DNA, heterochromatin, telomere, beetle, Tenebrionidae.

Mapping Unequal Crossing over Hotspot Region of Simple Sequence Repeat in Maize

2009 ◽  
Vol 35 (5) ◽  
pp. 958-961
Author(s):  
Ji-Hua TANG ◽  
Xi-Qing MA ◽  
Wen-Tao TENG ◽  
Jian-Bing YAN ◽  
Jing-Rui DAI ◽  
...  
Keyword(s):  
Simple Sequence Repeat ◽  
Crossing Over ◽  
Sequence Repeat ◽  
Unequal Crossing Over ◽  
Simple Sequence

scholarly journals UNEQUAL CROSSING OVER AT THE rRNA TANDON AS A SOURCE OF QUANTITATIVE GENETIC VARIATION IN DROSOPHILA

Genetics ◽  
1980 ◽  
Vol 95 (3) ◽  
pp. 727-742 ◽  
Author(s):  
R Frankham ◽  
D A Briscoe ◽  
R K Nurthen
Keyword(s):  
Genetic Variation ◽  
Selection Response ◽  
Crossing Over ◽  
Wild Type ◽  
X Chromosomes ◽  
Unequal Crossing Over ◽  
Quantitative Genetic ◽  
Y Chromosomes ◽  
Homozygous Line ◽  
Minimum Estimate

ABSTRACT Abdominal bristle selection lines (three high and three low) and controls were founded from a marked homozygous line to measure the contribution of sex-linked "mutations" to selection response. Two of the low lines exhibited a period of rapid response to selection in females, but not in males. There were corresponding changes in female variance, in heritabilities in females, in the sex ratio (a deficiency of females) and in fitness, as well as the appearance of a mutant phenotype in females of one line. All of these changes were due to bb alleles (partial deficiencies for the rRNA tandon) in the X chromosomes of these lines, while the Y chromosomes remained wild-type bb+. We argue that the bb alleles arose by unequal crossing over in the rRNA tandon.—A prediction of this hypothesis is that further changes can occur in the rRNA tandon as selection is continued. This has now been shown to occur.—Our minimum estimate of the rate of occurrence of changes at the rRNA tandon is 3 × 10-4. As this is substantially higher than conventional mutation rates, the questions of the mechanisms and rates of origin of new quantitative genetic variation require careful re-examination.

Unequal Crossing-over in Unique PABP2 Mutations in Japanese Patients

2002 ◽  
Vol 59 (3) ◽  
pp. 474 ◽  
Author(s):  
Mika Nakamoto ◽  
Satoshi Nakano ◽  
Shingo Kawashima ◽  
Masafumi Ihara ◽  
Yo Nishimura ◽  
...  
Keyword(s):  
Japanese Patients ◽  
Crossing Over ◽  
Unequal Crossing Over

scholarly journals Possible role of natural selection in the formation of tandem-repetitive noncoding DNA.

Genetics ◽  
1994 ◽  
Vol 136 (1) ◽  
pp. 333-341
Author(s):  
W Stephan ◽  
S Cho
Keyword(s):  
Natural Selection ◽  
Satellite Dna ◽  
Repeat Length ◽  
Crossing Over ◽  
Recombination Rates ◽  
Noncoding Dna ◽  
Satellite Dnas ◽  
Unequal Crossing Over ◽  
Wide Range ◽  
Long Range Ordering

Abstract A simulation model of sequence-dependent amplification, unequal crossing over and mutation is analyzed. This model predicts the spontaneous formation of tandem-repetitive patterns of noncoding DNA from arbitrary sequences for a wide range of parameter values. Natural selection is found to play an essential role in this self-organizing process. Natural selection which is modeled as a mechanism for controlling the length of a nucleotide string but not the sequence itself favors the formation of tandem-repetitive structures. Two measures of sequence heterogeneity, inter-repeat variability and repeat length, are analyzed in detail. For fixed mutation rate, both inter-repeat variability and repeat length are found to increase with decreasing rates of (unequal) crossing over. The results are compared with data on micro-, mini- and satellite DNAs. The properties of minisatellites and satellite DNAs resemble the simulated structures very closely. This suggests that unequal crossing over is a dominant long-range ordering force which keeps these arrays homogeneous even in regions of very low recombination rates, such as at satellite DNA loci. Our analysis also indicates that in regions of low rates of (unequal) crossing over, inter-repeat variability is maintained at a low level at the expense of much larger repeat units (multimeric repeats), which are characteristic of satellite DNA. In contrast, the microsatellite data do not fit the proposed model well, suggesting that unequal crossing over does not act on these very short tandem arrays.

Quantitative Analysis of C-bands in Chromosomes 1, 9, 16, and Y of Twins

1983 ◽  
Vol 32 (3-4) ◽  
pp. 257-260 ◽  
Author(s):  
Marise P. Pedrosa ◽  
F.M. Salzano ◽  
Margarete S. Mattevi ◽  
Judith Viégas
Keyword(s):  
Quantitative Analysis ◽  
Crossing Over ◽  
Same Sex ◽  
Genetic Determination ◽  
Unequal Crossing Over

Thirty-two pairs of Caucasoid twins, 16 monozygotic (MZ) and 16 dizygotic (DZ) of the same sex, were studied by densitometry in relation to the C-bands of chromosomes 1, 9, 16, and Y. Confirming earlier results, concordance was not absolute among MZ. Estimates of the degree of genetic determination for these traits varied from 0.73 to 0.89 for the autosomes and from 0.86 to 0.95 for the Y. There are now stronger indications that a fraction of the intergeneration variability found in these structures may be real, probably due to mitotic and/or meiotic unequal crossing-over.

MEIOTIC NONDISJUNCTION AND ANEUPLOIDS IN INTERSYNGENIC HYBRIDS OF PARAMECIUM CAUDATUM

Genetics ◽  
1985 ◽  
Vol 111 (4) ◽  
pp. 779-794
Author(s):  
Yuuji Tsukii ◽  
Koichi Hiwatashi
Keyword(s):  
Mating Type ◽  
Genetic Study ◽  
F1 Hybrids ◽  
Crossing Over ◽  
Paramecium Caudatum ◽  
Meiotic Process ◽  
Unequal Crossing Over ◽  
Meiotic Nondisjunction ◽  
Fertile Hybrids

ABSTRACT Artificially induced intersyngenic crosses in Paramecium caudatum can produce viable and fertile hybrids. When F1 hybrids of double E mating type (Mt  1/Mt  3 or Mt  12/Mt  3) were crossed with mating type O (mt/mt), aberrant segregants of double E and single O type were produced. This segregation was not explained by ordinary equal or unequal crossing over. Breeding analyses of these segregants by using linkage between Mt and cnrA (a behavioral mutant) revealed that they were produced by meiotic nondisjunction of bivalent chromosomes carrying Mt genes, and thus the double E and single O segregants were aneuploids: trisomics (Mt  1/Mt  3/mt or Mt  12/Mt  3/mt) and monosomics (mt), respectively. An aberrant segregant was also obtained for another locus, tnd 2, independent of both Mt and cnrA, suggesting the occurrence of meiotic nondisjunction throughout hybrid genomes. These aneuploids will be useful for genetic study in this species. The occurrence of meiotic nondisjunction in the intersyngenic hybrids also suggests that syngens of P. caudatum have been reproductively isolated for long enough to develop chromosomal incompatibility in their meiotic process.

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