Ecological and genetic factors contributing to the low frequency of male sterility in Chamaecrista Fasciculata (Fabaceae)

1998 ◽  
Vol 85 (9) ◽  
pp. 1243-1250 ◽  
Author(s):  
Holly L. Williams ◽  
Charles B. Fenster
Keyword(s):  
Male Sterility ◽  
Genetic Factors ◽  
Low Frequency ◽  
Chamaecrista Fasciculata

Low Frequency of Genetic Factors Gm(s) and Di(a) in Finland

1969 ◽  
Vol 19 (2) ◽  
pp. 180-184 ◽  
Author(s):  
Anja Tiilikainen ◽  
E. Ruoslahti ◽  
M. Seppälä ◽  
L. Mårtensson ◽  
Erna Van Loghem
Keyword(s):  
Genetic Factors ◽  
Low Frequency

-308 G > A of TNF-α gene promoter decreases the risk of multiple sclerosis: a meta-analysis

2010 ◽  
Vol 17 (6) ◽  
pp. 658-665 ◽  
Author(s):  
Yan Yang ◽  
Rulin Sun ◽  
Heng Yang ◽  
Fang Zheng ◽  
Feili Gong
Keyword(s):  
Multiple Sclerosis ◽  
Genetic Factors ◽  
Association Studies ◽  
Meta Analysis ◽  
Low Frequency ◽  
Gene Promoter ◽  
Tnf Α ◽  
Control Association ◽  
Necrosis Factor ◽  
Reduced Risk

Background: Environmental and genetic factors are thought to be involved in the pathogenesis of multiple sclerosis (MS). Polymorphisms of tumor necrosis factor (TNF)-α −308 were implicated in MS risk in several case–control association studies. However, the studies have shown inconsistent results. Objectives: To address the association of G/A polymorphisms of TNF-α −308 with MS risk by meta-analysis. Methods: Thirteen studies were included. Pooled odds ratios (ORs) together with 95% confidence intervals (CIs) were calculated. Results: A total of 1870 cases and 2769 controls were included in the meta-analysis. The pooled result indicated that −308 A allele is significantly associated with reduced risk of MS compared with −308 G allele (A vs. G, p = 0.022). The same pattern of the result was also obtained in the contrasts of AA + GA vs. GG ( p = 0.008) and GA vs. GG ( p = 0.007). For AA vs. GG or AA vs. GA + GG, no significant association was detected most likely caused by very low frequency or non-availability of homozygote genotype AA for all of the studies. Conclusions: TNF-α −308 A allele is associated with reduced risk of MS.

scholarly journals Partial male sterility and the evolution of nuclear gynodioecy in plants

2002 ◽  
Vol 80 (3) ◽  
pp. 187-195 ◽  
Author(s):  
STEWART T. SCHULTZ
Keyword(s):  
Genetic Variability ◽  
Male Sterility ◽  
Inbreeding Depression ◽  
Low Frequency ◽  
Genetic Models ◽  
Selfing Rate ◽  
Frequency Dependent Selection ◽  
Fitness Advantage ◽  
General Importance ◽  
Classical Models

Gynodioecy, a genetic dimorphism of females and hermaphrodites, is pertinent to an understanding of the evolution of plant gender, mating and genetic variability. Classical models of nuclear gynodioecy attribute the maintenance of the dimorphism to frequency-dependent selection in which the female phenotype has a fitness advantage at low frequency owing to a doubled ovule fertility. Here, I analyse explicit genetic models of nuclear gynodioecy that expand on previous work by allowing partial male sterility in combination with either fixed or dynamically evolving mutational inbreeding depression. These models demonstrate that partial male sterility causes fitness underdominance at the mating locus, which can prevent the spread of females. However, if partial male sterility is compensated by a change in selfing rate, overdominance at the mating locus can cause the spread of females. Overdominance at introduction of the male sterility allele can be caused by high inbreeding depression and a lower selfing rate in the heterozygote, by purging of mutations by a higher selfing rate in the heterozygote, and by low inbreeding depression and a higher selfing rate in the heterozygote. These processes might be of general importance in the maintenance of mating polymorphisms in plants.

scholarly journals Age and genetic background determine hybrid male sterility in house mice

2018 ◽  
Author(s):  
Samuel J. Widmayer ◽  
David L. Aylor
Keyword(s):  
Reproductive Isolation ◽  
Male Sterility ◽  
Genetic Factors ◽  
Inbred Strains ◽  
House Mice ◽  
Reproductive Barriers ◽  
Hybrid Male ◽  
Hybrid Male Sterility ◽  
Unique Type ◽  
Age Dependent

AbstractHybrid male sterility (HMS) is a unique type of reproductive isolation commonly observed between house mouse (Mus musculus) subspecies in the wild and in laboratory crosses. We identified hybrids that display three distinct trajectories of fertility despite having identical genotypes at the major HMS gene Prdm9 and the X Chromosome. In each case, we crossed female PWK/PhJ mice representative of the M.m.musculus subspecies to males from classical inbred strains representative of M.m.domesticus: 129S1/SvImJ, A/J, C57BL/6J, and DBA/2J. PWK129S1 males are always sterile, while PWKDBA2 males escape HMS. In addition, we observe age-dependent sterility in PWKB6 and PWKAJ males. These males are fertile between 15 and 35 weeks with moderate penetrance. These results point to multiple segregating HMS modifier alleles, some of which have an age-dependent mode of action. Age-dependent mechanisms could have broad implications for the maintenance of reproductive barriers in nature.Author SummaryTwo subspecies of house mice show partial reproductive barriers in nature, and may be in the process of speciation. We used mice derived from each subspecies to replicate hybrid male sterility (HMS) in laboratory mice. Two major genetic factors are well established as playing a role in mouse HMS, but the number of additional factors and their mechanisms are unknown. We characterized reproductive trait variation in a set of hybrid male mice that were specifically designed to eliminate the effects of known genetic factors. We discovered that age played an important role in fertility of some hybrids. These hybrid males showed a delayed onset of fertility, then became fertile for only a few weeks. Across all hybrids males in our study, we observed three distinct trajectories of fertility: complete fertility, complete sterility, and age-dependent fertility. These results point to two or more critical HMS variants with large enough effects to completely restore fertility. This study advances our understanding of the genetic architecture and biological mechanisms of reproductive isolation in mice.

Factor XIII Val34Leu variant and the risk of myocardial infarction

2007 ◽  
Vol 97 (04) ◽  
pp. 635-641 ◽  
Author(s):  
Mona Shafey ◽  
Josdalyne Anderson ◽  
Dimitri Scarvelis ◽  
Steven Doucette ◽  
France Gagnon ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Protective Effect ◽  
Factor Xiii ◽  
Genetic Factors ◽  
Reference Group ◽  
Data Extraction ◽  
Meta Analysis ◽  
Low Frequency ◽  
Protective Effects ◽  
Case Control Studies

SummaryGenetic factors are thought to contribute to the pathogenesis of acute myocardial infarction (AMI).A common variant of factor XIII (FXIII), FXIII Val34Leu, may be protective against developing an AMI, but various studies show conflicting results. We performed a meta-analysis to determine whether the FXIII Val34Leu variant is associated with a decreased risk of AMI. One hundred ninety-five articles were reviewed and 12 case-control studies were selected. We included studies involving patients with objectively diagnosed AMIs (WHO criteria), provided that FXIII Val34Leu genotyping data were available. Inclusion decisions, quality assessment, and data extraction were conducted by two reviewers. Hypothesizing that the Leu allele was protective, we performed three analyses with the Val/Val genotype as the reference group. Pooled odds ratios (OR) and their 95% confidence intervals (95% CI) were determined. Prior to pooling, heterogeneity testing was performed using the I 2 statistic. These studies included a total of 8,743 patients, of which 3,663 were AMI patients and 5,080 were healthy controls. Using the random effects methods, protective effects were seen with the Leu/Val genotype alone (OR 0.79, 95% CI 0.68–0.93) and with Leu/Val and Leu/Leu genotypes combined (OR 0.79, 95% CI 0.66–0.93).There was also a protective effect with the Leu/Leu genotype alone, (not statistically significant: OR 0.83, 95% CI 0.61–1.12), likely due to the low frequency of this genotype. These results suggest that there is an association between the factor XIII Leu allele and a modest protective effect against AMI and may provide useful information in profiling susceptibility to myocardial infarction.

Chromosome pairing affinities between Old and New World species of Bromus section Pnigma

1984 ◽  
Vol 62 (3) ◽  
pp. 581-585 ◽  
Author(s):  
K. C. Armstrong
Keyword(s):  
Chromosome Pairing ◽  
Interspecific Hybrids ◽  
New World ◽  
Genetic Factors ◽  
Low Frequency ◽  
World Species ◽  
The North ◽  
Evolutionary Pathways ◽  
Bromus Benekenii ◽  
Eurasian Species

A low frequency of allosyndetic chromosome pairing occurred in interspecific hybrids between species having large chromosomes (Bromus benekenii (Lange) Trimen, 2n = 4x = 28; B. ramosus Huds., 2n = 4x = 28; B. pacificus Shear, 2n = 4x = 28) and species having small chromosomes (B. erectus Huds., 2n = 4x = 28; B. inermis Leyss, 2n = 4x = 28; B. pumpellianus Scribn., 2n = 4x = 28; B. riparius Rehm, 2n = 10x = 70; and B. variegatus, 2n = 2x = 14). These results are consistent with the suggestion that the large (predominantly Eurasion) and small (predominantly American) chromosome species of section Pnigma have followed different evolutionary pathways. Chromosome pairing in interspecific hybrids revealed low affinities between the chromosomes of the Eurasian species B. ramosus and the North American species B. pacificus. Thus there was no evidence that B. ramosus contained a form of the L genome found in American species. However genetic factors suppressing homoeologous pairing could be present in the allotetraploid parents.

scholarly journals Practical Application of PCR-based Technology to Screen Texas Onion Breeding Lines for Cytoplasmic Male Sterility

HortScience ◽  
1997 ◽  
Vol 32 (4) ◽  
pp. 601B-601
Author(s):  
J. Alcala ◽  
J.F. Lopes ◽  
J.J. Giovannoni ◽  
L.M. Pike
Keyword(s):  
Cytoplasmic Male Sterility ◽  
Male Sterility ◽  
Low Frequency ◽  
Practical Application ◽  
Male Sterile ◽  
Chain Reaction ◽  
Breeding Lines ◽  
Specific Amplification ◽  
Efficient Alternative ◽  
Polymerase Chain

Identification and production of onion male-sterile and maintainer lines by conventional breeding takes between 4 to 8 years, due in part to the biennial nature of onion. In addition, male sterile plants and maintainer genotypes occur at a very low frequency in onion populations (Pike, 1986). A significantly shorter and more efficient alternative involves the screening of breeding lines for cytoplasmic male sterility using PCR-based technology. Thirty short-day onion breeding lines from the Texas A&M onion program were screened for type of cytoplasm (normal or sterile). Specific amplification of a fragment of chloroplast genome was achieved using the polymerase chain reaction according to Havey (1991). Forty-eight individual onion plants were screened per line. Out of thirty lines evaluated, 13 showed 100% sterile cytoplasm, 6 showed 100% normal cytoplasm, and 11 showed both types of cytoplasm. Lines showing normal cytoplasm or both cytoplasmic types were kept and reanalyzed. Only plants presenting normal cytoplasm were grown to maturity to help in the identification of maintainer lines as part of the Texas A&M onion breeding program.

scholarly journals Molecular genetic aspects of complicated myopia pathogenesis

2018 ◽  
Vol 11 (3) ◽  
pp. 48-56
Author(s):  
Alexey N. Kulikov ◽  
Sergey V. Churashov ◽  
Vladimir A. Reytuzov
Keyword(s):  
Refractive Error ◽  
Genetic Factors ◽  
Molecular Genetic ◽  
Low Frequency ◽  
Optical Power ◽  
Refractive Errors ◽  
Progressive Myopia ◽  
Remodeling Of Extracellular Matrix ◽  
The Impact ◽  
Modest Effect

Complicated myopia (CM) is not only a refractive error but a complex, multifactorial disorder characterized by a mismatch between the optical power of the eye and the axial length that causes the image to be focused off the retina. Genetic factors in progressive myopia play a key role in determining the impact of ecologic factors on refraction development. The majority of genetic variants underlying CM are characterized by modest effect and/or low frequency, which makes them difficult to identify using classic genetic approaches. The genes identified to date account for less than 10% of all myopia cases, suggesting the existence of a large number of yet unidentified low-frequency and/or small-effect variants, which underlie the majority of myopia cases. Genome analysis revealed dozens of loci associated with non-syndromic myopia, and showed that refractive errors are associated with mutations in genes that are involved in the growth and development of the eye by regulating ion transport, neurotransmission, remodeling of extracellular matrix of the retina and other ocular structures. Genetic study of refractive error provides a unique opportunity to detect key molecules that may play important roles in the development of refractive error. Identifying the molecular basis of refractive error helps to understand mechanisms, and subsequently to design rational therapeutic intervention for this condition.

scholarly journals The Male-Sterility Polymorphism of Silene vulgaris: Analysis of Genetic Data From Two Populations and Comparison With Thymus vulgaris

Genetics ◽  
1998 ◽  
Vol 150 (3) ◽  
pp. 1267-1282 ◽  
Author(s):  
D Charlesworth ◽  
Valérie Laporte
Keyword(s):  
Male Sterility ◽  
Genetic Factors ◽  
Natural Populations ◽  
Genetic Data ◽  
The Other ◽  
Thymus Vulgaris ◽  
Silene Vulgaris ◽  
Genetic Studies ◽  
Pollen Donor ◽  
Two Populations

Abstract Results are given of genetic studies of male sterility using plants from two natural populations from Sussex, England. Both populations have substantial frequencies of females, ∼0.25 in population 1 and 0.60 in population 3. As in the few other gynodioecious populations studied in detail, many genetic factors are present. In population 1, there are at least two, and more likely three, different cytoplasmic types, one of which appears to produce male sterility in progeny from any hermaphrodite pollen donor; in other words restorer alleles for this cytoplasm are rare or absent from the population. The other two populations can be carried in hermaphrodites that have the dominant restorers. In population 1, there are also probably three restorer loci with complementary recessive male-sterility alleles, as well as a locus with duplicate action, which cannot produce male sterility unless the plant is also homozygous for the recessive allele at another locus. The results from population 3 are quite similar, though there was no evidence in this population for an unrestored sterility cytoplasm. A similar joint nucleocytoplasmic model with multiple restorers fits data from Thymus vulgaris.

A Study on the Fine Structure of the Lateral Line Organ of the Sea Eel

1973 ◽  
Vol 31 ◽  
pp. 648-649
Author(s):  
K. Hama
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Lateral Line ◽  
Low Frequency ◽  
Sensory Cells ◽  
Apical Surface ◽  
Voltage Electron ◽  
Sensory Epithelia ◽  
Low Frequency Vibration ◽  
Transmission Electron

The lateral line organs of the sea eel consist of canal and pit organs which are different in function. The former is a low frequency vibration detector whereas the latter functions as an ion receptor as well as a mechano receptor.The fine structure of the sensory epithelia of both organs were studied by means of ordinary transmission electron microscope, high voltage electron microscope and of surface scanning electron microscope.The sensory cells of the canal organ are polarized in front-caudal direction and those of the pit organ are polarized in dorso-ventral direction. The sensory epithelia of both organs have thinner surface coats compared to the surrounding ordinary epithelial cells, which have very thick fuzzy coatings on the apical surface.

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