Haptoglobin: The Evolutionary Product of Duplication, Unequal Crossing Over, and Point Mutation

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.

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Unequal Crossing-over in Unique PABP2 Mutations in Japanese Patients

Archives of Neurology ◽

10.1001/archneur.59.3.474 ◽

2002 ◽

Vol 59 (3) ◽

pp. 474 ◽

Cited By ~ 21

Author(s):

Mika Nakamoto ◽

Satoshi Nakano ◽

Shingo Kawashima ◽

Masafumi Ihara ◽

Yo Nishimura ◽

...

Keyword(s):

Japanese Patients ◽

Crossing Over ◽

Unequal Crossing Over

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Unequal crossing-over accounts for the organization of Drosophila virilis rDNA insertions and the integrity of flanking 28S gene

Nature ◽

10.1038/296579a0 ◽

1982 ◽

Vol 296 (5857) ◽

pp. 579-581 ◽

Cited By ~ 4

Author(s):

Peter M. M. Rae

Keyword(s):

Drosophila Virilis ◽

Crossing Over ◽

Unequal Crossing Over

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

Genetics ◽

10.1093/genetics/136.1.333 ◽

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.

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

Acta geneticae medicae et gemellologiae twin research ◽

10.1017/s0001566000005122 ◽

1983 ◽

Vol 32 (3-4) ◽

pp. 257-260 ◽

Cited By ~ 6

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.

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MEIOTIC NONDISJUNCTION AND ANEUPLOIDS IN INTERSYNGENIC HYBRIDS OF PARAMECIUM CAUDATUM

Genetics ◽

10.1093/genetics/111.4.779 ◽

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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