Cytogenetics of the grasshopper Moraba scurra. 1. Meiosis of interracial and Interpopulation hybrids.

1957 ◽  
Vol 5 (3) ◽  
pp. 285 ◽  
Author(s):  
MJD White
Keyword(s):  
Chromosome Pair ◽  
Chiasma Formation ◽  
B Chromosome ◽  
Chromosome Race ◽  
F1 Hybrids ◽  
Completely Regular ◽  
Essentially Normal ◽  
Pericentric Inversions ◽  
History Of ◽  
Regular Meiosis

Numerous F1 hybrids between the races of Moraba scurra Rehn with 2nB = 15 and 2nB = 17 were reared in the laboratory and in artificial colonies established in nature. Most F1 males have almost completely regular meiosis, their chiasma frequency being essentially normal. These individuals show a trivalent, composed of an "A" and a "B" chromosome of the 17-chromosome race paired with the corresponding limbs of an "AB" chromosome derived from the 15-chromosome race. Disjunction of the trivalent is usually extremely regular. Occasionally either the A or the B chromosome fails to pair with the AB. In hybrid individuals which happen to have their CD chromosome pair heterozygous for the Blundell rearrangement (i.e. Standard/Blundell) the proximal end of the A chromosome is occasionally paired with the Blundell-carrying CD chromosome. This suggests that the evolutionary "dissociation" of the AB into separate A and B chromosomes, which is present in the 17-chromosome race, was not a simple fragmentation but a translocation involving a Blundell chromosome, and that the A chromosome received its centromere from the Blundell element. Various types of abnormal synapsis occur in hybrids between individuals from populations situated several hundred miles apart, even when both belong to the 15-chromosome race. Chiasma-formation in CD bivalents homozygous and heterozygous for the three known sequences of the CD chromosome (Standard, Blundell, Molonglo) suggests that Blundell and Molonglo are both related to Standard as pericentric inversions. The bearing of these data on the history of the species is discussed.

scholarly journals Paroxysmal head drops with ataxia-like symptoms presenting as Sandifer syndrome in a 3-year old girl

2020 ◽  
Vol 13 (3) ◽  
pp. e230989
Author(s):  
Abubakar Sharif ◽  
Lucinda Carr ◽  
Efstratios Saliakellis ◽  
Himadri Chakraborty
Keyword(s):  
Physical Examination ◽  
Single Fibre ◽  
Barium Swallow ◽  
Clavicular Fracture ◽  
Distal Oesophagus ◽  
Blood Tests ◽  
Language Therapist ◽  
Mri Brain ◽  
Essentially Normal ◽  
History Of

We present a case of Sandifer syndrome in a 3-year-old girl who initially presented with a history of recurrent paroxysmal head drops associated with ataxia-like symptoms and recurrent falls sustaining a clavicular fracture on one occasion. She was referred to and seen by the paediatric neurologist. Physical examination, electroencephalogram, MRI brain, electromyograph single fibre study and blood tests were all normal. With the history of hiccups and choking-like episodes she was referred to the speech and language therapist (SALT). SALT assessment did not reveal indications of swallowing impairment or possible aspiration. A barium swallow later showed small amount of reflux into the distal oesophagus. This prompted a trial of lansoprazole and she was referral to the gastroenterologists. Endoscopy and oesophageal manometry were essentially normal. However, the pH impedance study revealed severe gastro-oesophageal reflux disease. She continued with lansoprazole and dairy-free diet and her symptoms resolved.

scholarly journals Cytogenetic analysis of the 18S, 5S rDNA and B chromosome of Iheringichthys labrosus (Lütken, 1874) (Siluriformes, Pimelodidae)

2010 ◽  
Vol 70 (3) ◽  
pp. 631-636 ◽  
Author(s):  
RA. Carvalho ◽  
A. Laudicina ◽  
L. Giuliano-Caetano ◽  
IC. Martins-Santos ◽  
AL. Dias
Keyword(s):  
Chromosome Pair ◽  
Base Composition ◽  
5S Rdna ◽  
B Chromosome ◽  
Positive Staining ◽  
Strong Fluorescence ◽  
Terminal Position ◽  
Cytogenetic Analyses ◽  
Iheringichthys Labrosus ◽  
Ribosomal Dnas

Cytogenetic analyses of the location of 18S and 5S ribosomal DNAs, and the base composition of B chromosomes of Iheringichthys labrosus from Tibagi River, Paraná, Brazil, are provided. AgNORs were observed in the terminal position on the long arm of a subtelocentric chromosome pair. CMA3-positive staining was observed in some chromosomes, which besides being associated with NORs, were all DAPI-negative. Chromosome B showed a strong fluorescence with CMA3. The concomitant use of 18S and 5S rDNA probes using the FISH technique revealed 18S ribosomal cistrons in a pair of subtelocentric chromosomes, on the long arm in the terminal position, coinciding with the AgNOR. The 5S sites were found in another subtelocentric pair, on the long arm in the interstitial region, near the centromere. The findings of the present study suggest that, although there are some more conserved cytogenetic characteristics, populations of I. labrosus may show their own characteristics.

Use of RFLPs to determine the chromosome composition of tetraploid triticale (A/B)(A/B)RR

Genome ◽  
1995 ◽  
Vol 38 (2) ◽  
pp. 250-254 ◽  
Author(s):  
T. Lelley ◽  
E. Kazman ◽  
K. M. Devos ◽  
M. D. Gale
Keyword(s):  
Chromosome Pair ◽  
Fragment Length Polymorphism ◽  
Tetraploid Wheat ◽  
Selective Advantage ◽  
B Chromosome ◽  
Wheat Genome ◽  
Rflp Markers ◽  
Specific Chromosome ◽  
Genome Chromosome ◽  
B Genome

Tetraploid triticale, (A/B)(A/B)RR (2n = 28), is a botanical novelty, an amphiploid composed of a diploid rye and a 14 chromosome wheat genome made up of chromosomes of the A and B genomes of tetraploid wheat. Restriction fragment length polymorphism (RFLP) markers were used to elucidate the chromosome composition of the mixed wheat genome of 35 different tetraploid triticale lines. Of 128 possible A/B chromosome pair combinations, only 6 were found among these lines, with a prevalence of the 1A, 2A, 3B, 4B, 5B, 6B, and 7B karyotype. In most triticale lines stable wheat genomes made up of only homologous A or B genome chromosome pairs were identified, however, in some lines homoeologous chromosome pairs were found. In this paper we demonstrate that RFLPs can be used successfully as an alternative to C-banding for the identification of the chromosome composition of tetraploid triticale and discuss the possible selective advantage of specific chromosome composition.Key words: tetraploid triticale, mixed wheat genome, RFLR

scholarly journals Stable Species Boundaries Despite Ten Million Years of Hybridization in Tropical Eels

2019 ◽  
Author(s):  
Julia M. I. Barth ◽  
Chrysoula Gubili ◽  
Michael Matschiner ◽  
Ole K. Tørresen ◽  
Shun Watanabe ◽  
...  
Keyword(s):  
Sequence Data ◽  
F1 Hybrids ◽  
Species Boundaries ◽  
Hybrid Breakdown ◽  
Genome Wide ◽  
Dynamic Scenario ◽  
Stable Species ◽  
Species Pairs ◽  
History Of ◽  
Tropical Eels

AbstractGenomic evidence is increasingly underpinning that hybridization between taxa is commonplace, challenging our views on the mechanisms that maintain their boundaries. Here, we focus on seven catadromous eel species (genusAnguilla), and use genome-wide sequence data from more than 450 individuals sampled across the tropical Indo-Pacific, morphological information, and three newly assembled draft genomes to compare contemporary patterns of hybridization with signatures of past gene flow across a time-calibrated phylogeny. We show that the seven species have remained distinct entities for up to 10 million years, despite a dynamic scenario of incomplete isolation whereby the current frequencies of hybridization across species pairs (over 5% of all individuals were either F1 hybrids or backcrosses) contrast remarkably with patterns of past introgression. Based on near-complete asymmetry in the directionality of hybridization and decreasing frequencies of later-generation hybrids, we identify cytonuclear incompatibilities and hybrid breakdown as two powerful mechanisms that can support species cohesion even when hybridization has been pervasive throughout the evolutionary history of entire clades.

THE EFFECT OF ACCESSORY CHROMATIN ON CHIASMA DISTRIBUTION IN MAIZE

1976 ◽  
Vol 18 (3) ◽  
pp. 479-484 ◽  
Author(s):  
Edward J. Ward
Keyword(s):  
Zea Mays ◽  
Chiasma Frequency ◽  
Zea Mays L ◽  
Chiasma Formation ◽  
B Chromosome ◽  
Abnormal Chromosome ◽  
Chromosome 10 ◽  
Chiasma Distribution ◽  
Metaphase I

From an analysis of metaphase I bivalent configurations in Zea mays L. it was possible to determine the effects of two supernumerary elements on chiasma formation. Both the B chromosome and abnormal chromosome 10 increased chiasma frequency. In addition to enhancing total exchanges, both elements caused a redistribution of chiasmata from distal to more proximal locations.

A stably transmitted pair of translocated supernumerary chromosomes in maize

Genome ◽  
1995 ◽  
Vol 38 (3) ◽  
pp. 558-565 ◽  
Author(s):  
Marjorie P. Maguire
Keyword(s):  
Chiasma Formation ◽  
B Chromosome ◽  
Supernumerary Chromosome ◽  
Chromosome Segment ◽  
Crossing Over ◽  
Preferential Pairing ◽  
Supernumerary Chromosomes ◽  
Unknown Source ◽  
Chromosome Segments

A pair of stably transmitted supernumerary chromosomes of unknown source has been found in a maize stock carrying a desynaptic mutant. The presence of the supernumerary chromosome appears to be unrelated to the meiotic mutant, but is believed to have been derived from a translocated B chromosome contaminant. The supernumerary chromosomes carry a segment of a A chromosome in this stock where there appear to be two normal copies of each of the 10 A chromosomes. Thus, this A chromosome segment is present in quadruplicate. Surprisingly, a quadrivalent configuration is formed in most microsporocytes, which involves not only synapsis but also chiasma formation in the A chromosome segments involved in the quadrivalent. This represents a strong preferential pairing of supernumeraries with the normal A chromosome segments. Such nonrandom association and crossing over might provide information on the nature of early homologue alignment at meiosis.Key words: supernumerary chromosomes, modified B chromosome, BA translocation, preferential pairing and crossing over.

Factors affecting the meiotic pairing behaviour of B chromosomes in the grasshopper Eyprepocnemis plorans

1984 ◽  
Vol 26 (6) ◽  
pp. 664-668 ◽  
Author(s):  
N. Henriques-Gil ◽  
P. Arana ◽  
J. L. Santos
Keyword(s):  
Chiasma Frequency ◽  
Chiasma Formation ◽  
B Chromosome ◽  
B Chromosomes ◽  
Meiotic Pairing ◽  
Eyprepocnemis Plorans ◽  
Factors Affecting ◽  
Chiasma Localization ◽  
A Site ◽  
Pairing Behaviour

A study of the meiotic behaviour of different B-chromosome variants in the acridid grasshopper Eyprepocnemis plorans demonstrates that pairing and chiasma formation in these supernumerary chromosomes depend both on genotypic factors and on the structure of the B chromosomes themselves. Genotypic effects are evidenced by the differences in chiasma frequency which the same B-chromosome combinations show in different individuals. Structural effects can be inferred from the fact that 9 of the 14 known known B variants carry a unique site to which interstitial chiasmata are confined, whereas such a site is lacking in the other five variants.Key words: B chromosomes, C-bands, chiasma frequency, chiasma localization.

scholarly journals Electrolyte disorders in a young female following short-term omeprazole therapy

2018 ◽  
Vol 7 (5) ◽  
pp. 1040
Author(s):  
Collins Amadi ◽  
Emmanuel M. Owamagbe ◽  
Ugochukwu S. Duru
Keyword(s):  
Young Female ◽  
Laboratory Evaluation ◽  
Electrolyte Disorders ◽  
Laboratory Findings ◽  
Presenting Symptoms ◽  
Essentially Normal ◽  
Lower Extremity Muscle ◽  
Tingling Sensation ◽  
History Of ◽  
Plasma Magnesium

A 29 years old female presented to us in the metabolic clinic of the University of Port Harcourt Teaching Hospital (UPTH) on account of a week history of easy fatigability, weakness, and lower extremity muscle cramps associated with numbness and tingling sensation in the peri-oral area, fingers and toes. Two weeks prior to the onset of her presenting symptoms, she had visited a local pharmaceutical shop on account of a distressing epigastric discomfort and was subsequently placed on daily oral omeprazole 20mg daily for a month by a pharmacist. She had been on the omeprazole medication for two weeks before her present symptoms manifested. Her past medical history was not suggestive of hypoparathyroidism nor pancreatitis. She was married with three children and has an uneventful family, social and obstetric histories. On examination, she was a healthy well-oriented young female with positive Trousseau’s, Chvostek’s and epigastric tenderness signs. Further Laboratory evaluation revealed she had low plasma magnesium, low plasma albumin-corrected calcium, and low serum parathyroid hormone levels, while other laboratory parameters were essentially normal. A diagnosis of omeprazole-induced electrolyte disorders (hypomagnesaemia and hypocalcaemia) associated with hypoparathyroidism was made following the review of her clinical examination and laboratory findings. She was subsequently managed with oral magnesium supplements following the withdrawal of the omeprazole medication (replaced with oral ranitidine), monitored weekly, and full recovery was achieved after three weeks.

scholarly journals Meiotic Crossover Patterning

2021 ◽  
Vol 9 ◽  
Author(s):  
Nila M. Pazhayam ◽  
Carolyn A. Turcotte ◽  
Jeff Sekelsky
Keyword(s):  
Chromosome Segregation ◽  
Chromosome Pair ◽  
Double Strand Breaks ◽  
Current Understanding ◽  
Genetic Studies ◽  
Strand Breaks ◽  
Proper Number ◽  
Key Players ◽  
Meiotic Crossover ◽  
History Of

Proper number and placement of meiotic crossovers is vital to chromosome segregation, with failures in normal crossover distribution often resulting in aneuploidy and infertility. Meiotic crossovers are formed via homologous repair of programmed double-strand breaks (DSBs). Although DSBs occur throughout the genome, crossover placement is intricately patterned, as observed first in early genetic studies by Muller and Sturtevant. Three types of patterning events have been identified. Interference, first described by Sturtevant in 1915, is a phenomenon in which crossovers on the same chromosome do not occur near one another. Assurance, initially identified by Owen in 1949, describes the phenomenon in which a minimum of one crossover is formed per chromosome pair. Suppression, first observed by Beadle in 1932, dictates that crossovers do not occur in regions surrounding the centromere and telomeres. The mechanisms behind crossover patterning remain largely unknown, and key players appear to act at all scales, from the DNA level to inter-chromosome interactions. There is also considerable overlap between the known players that drive each patterning phenomenon. In this review we discuss the history of studies of crossover patterning, developments in methods used in the field, and our current understanding of the interplay between patterning phenomena.

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