Orientation and segregation of Robertsonian trivalents in Dichroplus pratensis (Acrididae)

Genome ◽  
1988 ◽  
Vol 30 (6) ◽  
pp. 947-955 ◽  
Author(s):  
Claudio J. Bidau ◽  
Patricia M. Mirol
Keyword(s):  
Chiasma Frequency ◽  
Centric Fusion ◽  
South American ◽  
Meiotic Segregation ◽  
Sperm Production ◽  
Position Effects ◽  
Balanced Polymorphism ◽  
Abnormal Sperm ◽  
Pairing Behavior ◽  
Different Populations

Pairing behavior, metaphase I orientation, and anaphase I segregation of centric fusion trivalents were studied in 26 single, 15 double, and 2 triple male fusion heterozygotes of the polymorphic South American melanopline grasshopper Dichroplus pratensis. They represent the seven different fusions and their combinations already described in different populations of the species. Our analysis showed the following: (1) pairing behavior is very regular in all trivalents; (2) frequencies of linear orientation was very low irrespective of the trivalent involved; (3) reorientation seems to occur frequently since frequencies of abnormal segregation and aneuploid second division cells were invariably lower than those of nonconvergent orientation; (4) aneuploidy and abnormal sperm production increases with increasing number of fusions; (5) chiasma frequency and localisation is relevant to trivalent orientation since trivalents with nonconvergent orientations showed proximal and interstitial chiasmata more frequently than convergently oriented ones. The results are in agreement with the hypothesis that these polymorphisms are old and stable, and confirm that for the maintenance of a balanced polymorphism, if this polymorphism is adaptive because of its consequences on recombination, position effects, etc., changes tending to stabilise trivalent orientation and segregation are central.Key words: Dichrophus pratensis, grasshopper, Robertsonian trivalent, meiotic orientation, meiotic segregation.

Seasonality of birth in India

1978 ◽  
Vol 10 (4) ◽  
pp. 409-421 ◽  
Author(s):  
R. P. Bernard ◽  
Rohit V. Bhatt ◽  
D. M. Potts ◽  
A. Padma Rao
Keyword(s):  
Heat Stress ◽  
High Temperature ◽  
Spontaneous Abortion ◽  
Seasonal Changes ◽  
Sperm Production ◽  
Coital Frequency ◽  
Abnormal Sperm ◽  
Summer Temperatures ◽  
Seasonality Of Birth ◽  
Extremes Of Temperature

SummaryThe conception rate in Baroda and Manipal, India, is lowest during the hottest weather. The greatest extremes are found in Baroda and, following high summer temperatures, there is a prolongation of low conception rates which may indicate that part or all of the effect is mediated through an effect on scrotal temperature. However, other factors may also be involved and a reduction of coital frequency is likely at extremes of temperature. Seasonal changes in abortion, stillbirths and prematurity are also observed. Changes in spontaneous abortion could be due to heat stress in the mother or possibly to abnormal sperm production at high temperature or to less frequent coitus, leading to embryonic defects.

Biosystematic study of hexaploids Elymus tschimganicus and E. glaucissimus. II. Interspecific hybridization and genomic relationship

Genome ◽  
1993 ◽  
Vol 36 (6) ◽  
pp. 1157-1168 ◽  
Author(s):  
Bao-Rong Lu ◽  
Kevin B. Jensen ◽  
Björn Salomon
Keyword(s):  
Interspecific Hybridization ◽  
General Pattern ◽  
The Other ◽  
South American ◽  
Genomic Relationship ◽  
Target Species ◽  
Species Relationship ◽  
Genomic Relationships ◽  
Pairing Behavior ◽  
Elymus Species

To investigate genomic relationships of Elymus tschimganicus (Drobov) Tzvelev (2n = 6x = 42, S1S2Y genomes) and E. glaucissimus (M. Pop.) Tzvelev (2n = 6x = 42, S1S2Y genomes), interspecific hybridizations of the two target species were carried out with 27 other Elymus species containing the SH, SY, SYH, SYP, SYW, and SH1H2 genomes, respectively, collected from different geographic regions. Chromosome pairing behavior was analyzed at metaphase I in 27 hybrids representing 23 hybrid combinations, and overall genomic relationships of the two target species with the other Elymus taxa were estimated. The study concluded that (i) interspecific hybridization was principally easy to perform between the Elymus species, but no general pattern of crossability was obtained, and all hybrids were completely sterile, (ii) the two species have a similar meiotic pattern in their hybrids with the other Elymus species, and (iii) species containing the SY, SYP, and SYH genomes have a generally higher level of genomic homology to the target species than those possessing the SH genomes, and the South American hexaploid with the SH1H2 genomes has the lowest level of genomic homology to the two target taxa.Key words: Elymus, interspecific hybridization, meiosis, genome, species relationship.

Spatial population structure: patterns of adaptation in populations of the water hyacinth grasshopper Cornops aquaticum (Bruner 1906)

2021 ◽  
pp. 1-13
Author(s):  
Pablo C. Colombo ◽  
Mónica Zelarayán ◽  
M. Celeste Franceschini ◽  
M. Isabel Remis
Keyword(s):  
Water Hyacinth ◽  
Biological Control Agent ◽  
Selection Effect ◽  
Centric Fusion ◽  
Control Agent ◽  
South American ◽  
Morphometric Traits ◽  
Bayesian Approaches ◽  
Karyotypic Variability ◽  
Insect Populations

Abstract The water hyacinth grasshopper Cornops aquaticum (Bruner 1906) constitutes an appropriate model to assess phenotypic and karyotypic variability in the context of differentiation and adaptation of insect populations because it occurs over a wide latitudinal range. This study represents a general analysis of phenotype, karyotype and molecular variation in native populations of C. aquaticum in South America. This is also relevant because this insect is considered a promising biological control agent of water hyacinth, a native South American aquatic plant but a pest in South Africa. Along Paraná and Uruguay River Basins, body size correlated negatively with latitude, and positively so with temperature and rainfall in both sexes. To test whether the chromosomal and phenotypic patterns were adaptive, we compared them with neutral microsatellite loci variation in populations from the medium and lower course of the Paraná River. Firstly, the lack of pairwise association between karyotype and phenotype distance matrixes with that of neutral loci suggested non-neutrality. Secondly, phenotypic differentiation for all morphometric traits (PST) was significantly larger than molecular differentiation (FST), indicating a prevailing divergence selection effect on the observed phenotypic patterns. Finally, the phenotypic and genotypic spatial structures – inferred from Bayesian approaches – were discordant: neutral genetic structure clustered together most populations except for the two southernmost, downstream ones, whereas phenotypic spatial structure groups together all the deltaic populations and singles out the two northernmost ones. The results suggest directional selection leading to higher centric fusion frequencies in the downstream populations and favouring morphometric optimal differences in relation to the environment.

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.

Karyotypes and meiosis of the Australian Tettigoniidae (Orthoptera) II. The genus Nanodectes Rentz (Tettigoniinae)*

1991 ◽  
Vol 5 (1) ◽  
pp. 33 ◽  
Author(s):  
N Ueshuma ◽  
DCF Rentz
Keyword(s):  
Chromosome Number ◽  
X Chromosome ◽  
Chromosome Evolution ◽  
Centric Fusion ◽  
Chromosome Rearrangements ◽  
Karyotypic Evolution ◽  
Telocentric Chromosome ◽  
Species Ranges ◽  
Tandem Fusion ◽  
Different Populations

The karyotypes and meioses from males of the species in the shield-backed katydid genus Nanodectes Rentz (Tettigoniinae) have been studied. The chromosome number of these species ranges from 2n = 15 to 2n =23 in the male. The male karyotypes were all X – 0 and the X was always the largest telocentric chromosome. Four types of chromosome systems are found in different populations of N. triodiae Rentz: 2n = 15 (6 metacentric + 8 telocentric autosomes + X), 2n = 15 (4 metacentric + 10 telocentric autosomes + X), 2n = 17 (4 metacentric+ 12 telocentric autosomes + X) and 2n = 19 (2 metacentric + 16 telocentric autosomes + X). Chromosome rearrangements, such as centric fusion and tandem fusion, appear to have played an important role in chromosome evolution at the inter- and intra-specific levels in Nanodectes. Possible pathways of karyotypic evolution and speciation are discussed.* Part I: pp. 303-51 in: 'The Tettigoniidae: Biology, Ecology, Systematics'. Eds W. J. Bailey and D. C. F. Rentz. (Crawford House: Bathurst.)

Meiotic studies of some Aegilops (Poaceae) species and populations in Iran

1999 ◽  
Vol 56 (3) ◽  
pp. 405-419 ◽  
Author(s):  
M. Sheidai ◽  
A. M. Saeed ◽  
B. Zehzad
Keyword(s):  
Cluster Analysis ◽  
Chromosome Number ◽  
Chiasma Frequency ◽  
Mother Cell ◽  
Cell Formation ◽  
Chromosome Elimination ◽  
Tetraploid Species ◽  
Unreduced Pollen ◽  
Chromosomal Association ◽  
Different Populations

Thirteen populations of three Aegilops (Poaceae) species were analysed for meiotic characters including chiasma frequency and distribution, as well as chromosomal association and segregation. Populations of A. triuncialis and A. cylindrica possessed n= 14 chromosome number (tetraploid) while populations of A. umbellulata possessed n = 7 (diploid). Tetraploid species showed diplontic behavior and formed bivalents only. Cluster analysis of meiotic data showed distinctness of the species, although variations were observed in the chiasma frequency and distribution among different populations of each species. Cytomixis and chromosome elimination led to ancuploid and unreduced pollen mother cell formation in the species studied.

scholarly journals The strategic reference gene: an organismal theory of inclusive fitness

2019 ◽  
Vol 286 (1904) ◽  
pp. 20190459 ◽  
Author(s):  
Lutz Fromhage ◽  
Michael D. Jennions
Keyword(s):  
Reference Gene ◽  
Evolutionary Theory ◽  
Inclusive Fitness ◽  
Meiotic Segregation ◽  
Sperm Production ◽  
Offspring Production ◽  
Term Evolution ◽  
Counter Selection ◽  
As If

How to define and use the concept of inclusive fitness is a contentious topic in evolutionary theory. Inclusive fitness can be used to calculate selection on a focal gene , but it is also applied to whole organisms . Individuals are then predicted to appear designed as if to maximize their inclusive fitness, provided that certain conditions are met (formally when interactions between individuals are ‘additive’). Here we argue that applying the concept of inclusive fitness to organisms is justified under far broader conditions than previously shown, but only if it is appropriately defined. Specifically, we propose that organisms should maximize the sum of their offspring ( including any accrued due to the behaviour/phenotype of relatives), plus any effects on their relatives' offspring production, weighted by relatedness. By contrast, most theoreticians have argued that a focal individual's inclusive fitness should exclude any offspring accrued due to the behaviour of relatives. Our approach is based on the notion that long-term evolution follows the genome's ‘majority interest’ of building coherent bodies that are efficient ‘vehicles’ for gene propagation. A gene favoured by selection that reduces the propagation of unlinked genes at other loci (e.g. meiotic segregation distorters that lower sperm production) is eventually neutralized by counter-selection throughout the rest of the genome. Most phenotypes will therefore appear as if designed to maximize the propagation of any given gene in a focal individual and its relatives.

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