Synapsis and recombination in inversion heterozygotes

2010 ◽  
Vol 38 (6) ◽  
pp. 1676-1680 ◽  
Author(s):  
Anna A. Torgasheva ◽  
Pavel M. Borodin
Keyword(s):  
Genetic Background ◽  
Inverted Region ◽  
Meiotic Progression ◽  
High Incidence ◽  
Inversion Loop

Inversion heterozygotes are expected to suffer from reduced fertility and a high incidence of chromosomally unbalanced gametes due to recombination within the inverted region. Non-homologous synapsis of the inverted regions can prevent recombination there and diminish the deleterious effects of inversion heterozygosity. The choice between non-homologous and homologous synapsis depends on the size of inversion, its genetic content, its location in relation to the centromere and telomere, and genetic background. In addition, there is a class of inversions in which homologous synapsis is gradually replaced by non-homologous synapsis during meiotic progression. This process is called synaptic adjustment. The degree of synaptic adjustment depends critically on the presence and location of the COs (crossovers) within the inversion loop. Only bivalents without COs within the loop and those with COs in the middle of the inversion can be completely adjusted and became linear.

Synaptonemal complex spreading in Allium ursinum: pericentric asynapsis and axial thickenings

1987 ◽  
Vol 87 (3) ◽  
pp. 439-448
Author(s):  
J. Loidl
Keyword(s):  
Synaptonemal Complex ◽  
Inhibitory Effect ◽  
Proximal Region ◽  
High Rate ◽  
Meiotic Pairing ◽  
Loop Formation ◽  
Allium Ursinum ◽  
High Incidence ◽  
Pairing Initiation ◽  
Inversion Loop

In Allium ursinum meiotic pairing of homologues is always incomplete; a proximal region on each bivalent remains regularly unsynapsed even in late pachytene. The spatial correlation of the unsynapsed region with the kinetochore suggests that the kinetochore itself exerts an inhibitory effect on synapsis in its vicinity. This can be interpreted as the cytological basis of the ‘centromere effect’ on recombination in this species. Moreover, the high incidence of a pericentric inversion loop in a heterozygous chromosome pair shows that proximal pairing initiation is possible and that its failure cannot be responsible for pericentric asynapsis. The formation of the inversion loop is complicated by the need for two independent pairing initiation sites because synapsis cannot proceed across the pericentric region. It is proposed that the meiotic bouquet polarization helps in establishing the presynaptic alignment of the homologous sites within the inverted regions and hence to achieve a high rate of inversion loop formation. Thickenings of the axial/lateral elements are not distributed equally along the synaptonemal complex. They are underrepresented in unpaired axes but strikingly abundant at the borders with synapsed regions, suggesting their origin in the pairing forks during the process of synapsis. They are virtually always present at nucleolus-organizing regions and often they appear at corresponding sites on opposite lateral elements. Besides the thickenings several other kinds of axial deformities are present in unpaired axes.

scholarly journals Deletion of Ku70, Ku80, or Both Causes Early Aging without Substantially Increased Cancer

2007 ◽  
Vol 27 (23) ◽  
pp. 8205-8214 ◽  
Author(s):  
Han Li ◽  
Hannes Vogel ◽  
Valerie B. Holcomb ◽  
Yansong Gu ◽  
Paul Hasty
Keyword(s):  
Genetic Background ◽  
Double Mutant ◽  
Severe Combined Immunodeficiency ◽  
Nonhomologous End Joining ◽  
Mutant Mice ◽  
Combined Immunodeficiency ◽  
End Joining ◽  
High Incidence ◽  
Early Aging ◽  
Increased Sensitivity

ABSTRACT Ku70 forms a heterodimer with Ku80, called Ku, that is critical for repairing DNA double-stand breaks by nonhomologous end joining and for maintaining telomeres. Mice with either gene mutated exhibit similar phenotypes that include increased sensitivity to ionizing radiation and severe combined immunodeficiency. However, there are also differences in the reported phenotypes. For example, only Ku70 mutants are reported to exhibit a high incidence of thymic lymphomas while only Ku80 mutants are reported to exhibit early aging with very low cancer levels. There are two explanations for these differences. First, either Ku70 or Ku80 functions outside the Ku heterodimer such that deletion of one is not identical to deletion of the other. Second, divergent genetic backgrounds or environments influence the phenotype. To distinguish between these possibilities, the Ku70 and Ku80 mutations were crossed together to generate Ku70, Ku80, and double-mutant mice in the same genetic background raised in the same environment. We show that these three cohorts have similar phenotypes that most resemble the previous report for Ku80 mutant mice, i.e., early aging without substantially increased cancer levels. Thus, our observations suggest that the Ku heterodimer is important for longevity assurance in mice since divergent genetic backgrounds and/or environments likely account for these previously reported differences.

scholarly journals Transcriptomic analysis of fetal membranes reveals pathways involved in preterm birth

2018 ◽  
Author(s):  
Silvana Pereyra ◽  
Claudio Sosa ◽  
Bernardo Bertoni ◽  
Rossana Sapiro
Keyword(s):  
Preterm Birth ◽  
Genetic Background ◽  
Fetal Membranes ◽  
South American ◽  
Common Pathway ◽  
South American Population ◽  
High Incidence ◽  
Different Populations ◽  
Term Births ◽  
Gestational Tissues

AbstractPreterm birth (PTB), defined as infant delivery before 37 weeks of completed gestation, results of the interaction of both genetic and environmental components and constitutes a complex multifactorial syndrome. Transcriptome analysis of PTB has proved challenging because of the multiple causes of PTB and the numerous maternal and fetal gestational tissues that must interact to facilitate parturition. A common pathway of labor and PTB may be the activation of fetal membranes. In this work, chorioamnion membranes from severe preterm and term fetus were analyzed using RNA sequencing. A total of 270 genes were differentially expressed (DE): 252 were up-regulated and 18 were down-regulated in the severe preterm compared to the term births. We found great gene expression homogeneity in the control samples, and not in severe preterm samples. In this work, we identified up-regulated pathways that were previously suggested as leading to PTB like immunological and inflammatory paths. New pathways that were not identified in preterm like the hemopoietic path appeared up-regulated in preterm membranes. A group of 18 down-regulated genes discriminates between term and severe preterm cases. These genes potentially characterize a severe preterm transcriptome pattern and therefore are candidate genes for understanding the syndrome. Some of the down-regulated genes are involved in the nervous system, morphogenesis (WNT-1, DLX5, PAPPA2) and ion channel complexes (KCNJ16, KCNB1), making them good candidates as biomarkers of PTB.The identification of this DE gene pattern may help to develop a multi-gene disease classifier. These markers were generated in an admixtured South American population where PTB has a high incidence. Since genetic background may impact differentially in different populations it is mandatory to include populations like South American and African ones that are usually excluded from high throughput approaches. These classifiers should be compared to those in other populations to get a global landscape of PTB.

scholarly journals Elements of the S-gene complex

1964 ◽  
Vol 5 (3) ◽  
pp. 397-409 ◽  
Author(s):  
Kamla Kant Pandey
Keyword(s):  
Gene Structure ◽  
Genetic Background ◽  
Normal Rate ◽  
Cultivated Plants ◽  
Nicotiana Alata ◽  
Gene Complex ◽  
High Incidence ◽  
Differential Behaviour ◽  
Dual Action ◽  
Different Sources

Cultivated plants of Nicotiana alata are self-incompatible and are of two kinds: normal (N); and exceptional (M). N plants are reciprocally compatible with N. langsdorffii; M plants are compatible only as males. M plants contain an unusual allele, SFI, which has a dual action in the style: it rejects both self-pollen, and Sf pollen from N. langsdorffii. The overall results agree with the assumption that the SFI gene produces two kinds of specificity in the style: primary specificity, which is responsible for the rejection of Sf pollen; and secondary specificity, which is responsible for the rejection of self-pollen as in SI alleles generally. The genetic sub-units concerned must be closely linked; there was no evidence for their dissociation in the 599 plants studied.In both compatible and incompatible pollinations, SFI pollen grows more slowly than SI and, in addition, appears to depress the normal rate of growth of SI pollen. In consequence, crosses SfSf × SISFI ♂ yielded significantly fewer S.I. plants than the 50% expected. The two kinds of pollen grew at comparable rates, however, when F1 (M × M) plants involving parents from different original sources were backcrossed to SfSf ♀. Progenies then showed the expected 1:1 ratio of S.I. to S.C. plants. These results are assumed to be due to differential behaviour of the SFI allele according to its genetic background. The change in background would be from a degree of homozygosity, in plants from the same source, to a degree of heterozygosity, in crosses between plants from different sources.The high incidence of the SFI gene in N. alata is considered to be due to the advantage it confers on a self-incompatible population when it is overlapping with a related self-compatible population (having the Sf gene). Plants carrying an SFI allele, by rejecting the Sf pollen, will restrict the spread of inbreeding and so be favoured by selection.The origin of the SFI and Sf alleles are discussed in relation to the author's hypothesis of S-gene structure.

scholarly journals The E mu-myc transgenic mouse. A model for high-incidence spontaneous lymphoma and leukemia of early B cells.

1988 ◽  
Vol 167 (2) ◽  
pp. 353-371 ◽  
Author(s):  
A W Harris ◽  
C A Pinkert ◽  
M Crawford ◽  
W Y Langdon ◽  
R L Brinster ◽  
...  
Keyword(s):  
B Cells ◽  
Cell Surface ◽  
Genetic Background ◽  
Constitutive Expression ◽  
Surface Markers ◽  
Cell Surface Markers ◽  
Lymphoid Leukemia ◽  
High Incidence ◽  
Myc Gene ◽  
Transplantation Assay

Mice transgenic for a c-myc gene driven by the IgH enhancer (E mu-myc) were shown to almost invariably develop lymphomas, 90% succumbing in the first 5 mo of life. The tumors typically presented as rapidly progressive lymphadenopathy with thymic involvement and were highly malignant by transplantation assay. Morphologically, they were lymphoblastic lymphomas, usually accompanied by lymphoid leukemia and granulocytosis, and were distinct from the tumors that arose much later in 37% of nontransgenic mice of the same (C57BL/6 x SJL)F2 genetic background. Cell-surface markers on 31 E mu-myc tumors identified 52% as pre-B lymphomas, 29% as mixed pre-B and B lymphomas, and 19% as B lymphomas. The tumors appeared to arise at random from a population of pre-B cells expanded by constitutive expression of the myc transgene. A majority of the animals initiated malignancy at the rate of 17% per week. The rate at which the cycling, benign pre-B cells spontaneously convert to malignancy was estimated to about 10(-10) per cell per generation. A transient leukocytosis identified in young E mu-myc mice was developed into a rapid assay for inheritance of the transgene.

scholarly journals Genetic Background of Congenital Chloride Diarrhea in High-Incidence Populations: Finland, Poland, and Saudi Arabia and Kuwait

1998 ◽  
Vol 63 (3) ◽  
pp. 760-768 ◽  
Author(s):  
Pia Höglund ◽  
Mari Auranen ◽  
Jerzy Socha ◽  
Kataryna Popinska ◽  
Hisham Nazer ◽  
...  
Keyword(s):  
Saudi Arabia ◽  
Genetic Background ◽  
Congenital Chloride Diarrhea ◽  
High Incidence

scholarly journals A review on ocular findings in mouse lemurs: potential links to age and genetic background

2017 ◽  
Vol 4 (2) ◽  
pp. 215-228 ◽  
Author(s):  
Marko Dubicanac ◽  
Ute Radespiel ◽  
Elke Zimmermann
Keyword(s):  
Genetic Background ◽  
Treatment Options ◽  
Clinical Signs ◽  
Mouse Lemur ◽  
Ocular Diseases ◽  
Comprehensive Overview ◽  
Aging Research ◽  
Ocular Findings ◽  
High Incidence ◽  
Mouse Lemurs

Abstract. Mouse lemurs, the world's smallest primates, inhabit forests in Madagascar. They are nocturnal, arboreal and dependent on vision for their everyday lives. In the last decades, the grey mouse lemur became increasingly important for biomedical research, in particular aging research. Experiments which require the combination of visual fitness and old age consequently depend on a solid knowledge of ocular pathologies. Although ocular diseases in mouse lemurs have been described as being common, they have not received much attention so far. Yet it is important to know when and why ocular diseases in captive mouse lemurs may occur. This review aims to provide a comprehensive overview of known ocular findings in mouse lemurs. It summarizes the frequency of ocular findings in captive mouse lemur colonies and points to their likely causes and treatment options based on the evidence available from other animals and humans. In addition, it shall be discussed whether age or genetic background may affect their development. This review may be used as a reference for future studies which require an assessment of visual performance in mouse lemurs and help to evaluate observed clinical signs and ocular diseases. Furthermore, the high incidence of specific diseases may provide new perspectives and set the groundwork for a new animal model for ocular research.

Computer Reconstruction of the Cellular Architecture of the Daphnia Magna Optic Ganglion

1975 ◽  
Vol 33 ◽  
pp. 284-285
Author(s):  
E. R. Macagno ◽  
C. Levinthal
Keyword(s):  
Daphnia Magna ◽  
Genetic Background ◽  
Compound Eye ◽  
Synaptic Connectivity ◽  
Serial Sections ◽  
Cross Sectional ◽  
Small Crustacean ◽  
Optic Ganglion ◽  
Structural Invariance ◽  
High Degree

The optic ganglion of Daphnia Magna, a small crustacean that reproduces parthenogenetically contains about three hundred neurons: 110 neurons in the Lamina or anterior region and about 190 neurons in the Medulla or posterior region. The ganglion lies in the midplane of the organism and shows a high degree of left-right symmetry in its structures. The Lamina neurons form the first projection of the visual output from 176 retinula cells in the compound eye. In order to answer questions about structural invariance under constant genetic background, we have begun to reconstruct in detail the morphology and synaptic connectivity of various neurons in this ganglion from electron micrographs of serial sections (1). The ganglion is sectioned in a dorso-ventra1 direction so as to minimize the cross-sectional area photographed in each section. This area is about 60 μm x 120 μm, and hence most of the ganglion fit in a single 70 mm micrograph at the lowest magnification (685x) available on our Zeiss EM9-S.

The observation of defects on (100) CdTe surfaces by chemical etching

1992 ◽  
Vol 50 (2) ◽  
pp. 1424-1425
Author(s):  
M.E. Lee
Keyword(s):  
Single Crystal ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Chemical Etching ◽  
Crystalline Perfection ◽  
Crystalline Defects ◽  
High Incidence ◽  
Crystallographic Defects ◽  
Cdznte Substrates ◽  
Device Technology

The crystalline perfection of bulk CdTe substrates plays an important role in their use in infrared device technology. The application of chemical etchants to determine crystal polarity or the density and distribution of crystallographic defects in (100) CdTe is not well understood. The lack of data on (100) CdTe surfaces is a result of the apparent difficulty in growing (100) CdTe single crystal substrates which is caused by a high incidence of twinning. Many etchants have been reported to predict polarity on one or both (111) CdTe planes but are considered to be unsuitable as defect etchants. An etchant reported recently has been considered to be a true defect etchant for CdTe, MCT and CdZnTe substrates. This etchant has been reported to reveal crystalline defects such as dislocations, grain boundaries and inclusions in (110) and (111) CdTe. In this study the effect of this new etchant on (100) CdTe surfaces is investigated.The single crystals used in this study were (100) CdTe as-cut slices (1mm thickness) from Bridgman-grown ingots.

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