Meiotic stability of B chromosomes and production of macrospermatids in Aiolopus strepens (Orthoptera: Acrididae)

Genome ◽  
1987 ◽  
Vol 29 (1) ◽  
pp. 5-10 ◽  
Author(s):  
J. A. Suja ◽  
C. Garcia de la Vega ◽  
J. S. Rufas
Keyword(s):  
Key Words ◽  
Natural Populations ◽  
B Chromosomes ◽  
Supernumerary Chromosomes ◽  
Mitotic Instability ◽  
Meiotic Stability ◽  
Intercellular Connections

Four males from several Spanish natural populations of Aiolopus strepens were found to carry B chromosomes. These are short and acrocentric and are identical in the different individuals. They show mitotic instability and meiotic stability. When present in odd numbers one unpaired B is generally observed, while in even numbers they usually form bivalents. In no case were lagging B's observed. B chromosomes do not affect nucleolar expression. A significant increase in the number of macrospermatids is found in individuals with B's. This is more pronounced in follicles containing odd numbers of supernumerary chromosomes. A possible explanation based on an assumed influence of B univalents on the maintenance of intercellular connections is discussed. Key words: B chromosomes, spermiogenesis, insect cytogenetics.

scholarly journals B Chromosomes in Free-Living Flatworms of the Genus Macrostomum (Platyhelminthes, Macrostomorpha)

2021 ◽  
Vol 22 (24) ◽  
pp. 13617
Author(s):  
Kira S. Zadesenets ◽  
Nikolay B. Rubtsov
Keyword(s):  
Genome Duplication ◽  
Natural Populations ◽  
B Chromosome ◽  
Laboratory Culture ◽  
B Chromosomes ◽  
Free Living ◽  
Transmission Rates ◽  
Supernumerary Chromosomes

B chromosomes (Bs) or supernumerary chromosomes are extra chromosomes in the species karyotype that can vary in its copy number. Bs are widespread in eukaryotes. Usually, the Bs of specimens collected from natural populations are the object of the B chromosome studies. We applied another approach analyzing the Bs in animals maintained under the laboratory conditions as lines and cultures. In this study, three species of the Macrostomum genus that underwent a recent whole-genome duplication (WGD) were involved. In laboratory lines of M. lignano and M. janickei, the frequency of Bs was less than 1%, while in the laboratory culture of M. mirumnovem, it was nearer 30%. Their number in specimens of the culture varied from 1 to 14. Mosaicism on Bs was discovered in parts of these animals. We analyzed the distribution of Bs among the worms of the laboratory cultures during long-term cultivation, the transmission rates of Bs in the progeny obtained from crosses of worms with different numbers of Bs, and from self-fertilized isolated worms. The DNA content of the Bs in M. mirumnovem was analyzed with the chromosomal in situ suppression (CISS) hybridization of microdissected DNA probes derived from A chromosomes (As). Bs mainly consisted of repetitive DNA. The cytogenetic analysis also revealed the divergence and high variation in large metacentric chromosomes (LMs) containing numerous regions enriched for repeats. The possible mechanisms of the appearance and evolution of Bs and LMs in species of the Macrostomum genus were also discussed.

Polysomy and supernumerary chromosomes in Ornithogalum umbellatum L. (Liliaceae)

Genome ◽  
1987 ◽  
Vol 29 (1) ◽  
pp. 19-25 ◽  
Author(s):  
C. Ruiz Rejón ◽  
R. Lozano ◽  
M. Ruiz Rejón
Keyword(s):  
Key Words ◽  
Natural Population ◽  
Sierra Nevada ◽  
High Frequency ◽  
Variable Number ◽  
B Chromosomes ◽  
Structural Variants ◽  
Satellite Chromosome ◽  
Supernumerary Chromosomes ◽  
Numerical Variation

One hundred bulbs of Ornithogalum umbellatum L. have been analyzed cytogenetically in one natural population collected from the Sierra Nevada of Spain. Three types of plants were identified: (i) diploid plants (2n = 18, 26%); (ii) diploid plants with a variable number of B chromosomes (1–8 B's, 40%); and (iii) polysomic plants (2n = 19–23) with or without B's (34%). B's are of two types: metacentric and acrocentric and are associated with three types of abnormalities: (i) failure of the A chromosomes to move to the poles at anaphase I; (ii) nondisjunction of some A chromosomes at anaphase II; and (iii) the occurrence of tetraploid sporocytes. The B's are isopycnotic, do not associate with the A's, and invariably occur as univalents at first meiosis but show no tendency for elimination. All members of the complement except the satellite chromosome, no. 6, have been detected in a trisomic or a tetrasomic condition. Additionally some unusual structural variants, not present in the diploid standard complement, appear in some polysomic individuals. The polysomic elements are euchromatic, stable, and they do not associate either with normal chromosomes or with B's. The polysomic elements form univalents when they are trisomic and bivalents when tetrasomic. The fact that a high frequency (94%) of the polysomic elements also carry B's suggests that these two forms of numerical variation are interrelated in origin. Key words: Ornithogalum umbellatum, polysomy, supernumerary chromosomes.

scholarly journals B Chromosomes in Free-Living Flatworms of the Genus Macrostomum (Platyhelminthes, Macrostomorpha)

2021 ◽  
Author(s):  
Kira S. Zadesenets ◽  
Nikolay B. Rubtsov
Keyword(s):  
Genome Duplication ◽  
Natural Populations ◽  
Laboratory Culture ◽  
B Chromosomes ◽  
Free Living ◽  
Transmission Rates ◽  
Supernumerary Chromosomes ◽  
Laboratory Cultures

B chromosomes (Bs) or supernumerary chromosomes are extra chromosomes in the species karyotype that can vary in their copy number. Bs are widespread. Usually, the Bs of specimens collected from natural populations are involved in studies. We applied another approach analyzing the Bs in animals of laboratory cultures. In this study, three species of the Macrostomum genus that underwent a recent whole-genome duplication (WGD) were involved. In laboratory lines of M. lignano and M. janickei, the frequency of Bs was less than 1%, while in the laboratory culture of M. mirumnovem, it was nearer 30%. Their number in specimens of the culture varied from 1 to 14. Mosaicism on Bs was discovered in parts of these animals. We analyzed the distribution of Bs among the worms of the laboratory cultures during long-term cultivation, the transmission rates of Bs in the progeny obtained from crosses of worms with different numbers of Bs, and from self-fertilized isolated worms. The DNA content of the Bs in M. mirumnovem was analyzed with the chromosomal in situ suppression (CISS) hybridization of microdissected DNA probes derived from A chromosomes (As). Bs mainly consisted of repetitive DNA. The cytogenetic analysis also revealed the divergence and high variation in large metacentric chromosomes (LMs) containing numerous regions enriched for repeats. The possible mechanisms of the appearance and evolution of Bs and LMs in species of the Macrostomum genus were also discussed.

Transmission analysis of mitotically unstable B chromosomes in Locusta migratoria

Genome ◽  
1994 ◽  
Vol 37 (6) ◽  
pp. 1027-1034 ◽  
Author(s):  
M. C. Pardo ◽  
M. D. López-León ◽  
J. Cabrero ◽  
J. P. M. Camacho
Keyword(s):  
Germ Line ◽  
Current Knowledge ◽  
Locusta Migratoria ◽  
Sexual Transmission ◽  
Natural Populations ◽  
Meiotic Drive ◽  
B Chromosome ◽  
B Chromosomes ◽  
The Other ◽  
Mitotic Instability

Seventeen controlled crosses in which the mitotically unstable B chromosome of Locusta migratoria was carried by one parent only have provided evidence that B chromosomes are significantly eliminated during sexual transmission in males, at a mean rate that almost counteracts the premeiotic accumulation derived from mitotic instability during germ line development. On the other hand, B chromosomes are significantly accumulated in females, presumably by their preferential migration to the secondary oocyte during the first meiotic division. These results substantially change the current knowledge about this B chromosome system, because the main B accumulation occurs in females and not in males, as was hitherto thought. Furthermore, this case shows that the maintenance of a single B system in natural populations may be the result of many different forces and mechanisms acting for and against B chromosomes.Key words: locust, Locusta migratoria, B chromosomes, accumulation mechanisms, meiotic drive, B elimination, parthenogenesis.

Occurrence and Origin of Supernumerary Chromosomes in Partamona (Hymenoptera: Apidae: Meliponini)

2016 ◽  
Vol 150 (1) ◽  
pp. 68-75 ◽  
Author(s):  
Diana P. Machado ◽  
Elder A. Miranda ◽  
Mariana C. Dessi ◽  
Camila P. Sabadini ◽  
Marco A. Del Lama
Keyword(s):  
High Frequency ◽  
Scar Marker ◽  
Sequence Data ◽  
Low Frequency ◽  
B Chromosomes ◽  
First Report ◽  
Supernumerary Chromosomes

Samples from 861 colonies of 12 Partamona species from 125 Brazilian localities were analysed for a SCAR marker specific to the B chromosomes of P. helleri. We identified the SCAR marker in 6 of the 12 species analysed, including 2 (P. gregaria and P. chapadicola) from the pearsoni clade. This is the first report on the presence of this marker in Partamona species that are not included in the cupira clade, which indicates that the B chromosomes probably are more widespread in this genus than previously thought. The analysis revealed a high frequency of the SCAR marker in the samples of P. helleri (0.47), P. cupira (0.46), and P. rustica (0.29), and a low frequency in P. aff. helleri (0.06). The frequency of the marker in P. helleri was correlated with the latitude of the sampling locality, decreasing from north to south. Sequence data on the SCAR marker from 50 individuals of the 6 species in which the presence of this marker was shown revealed a new scenario for the origin of the B chromosomes in Partamona.

Structural hybridity and supernumerary chromosomes in a diploid Tradescantia hirsuticaulis

1975 ◽  
Vol 53 (5) ◽  
pp. 456-465 ◽  
Author(s):  
C. C. Chinnappa
Keyword(s):  
Reciprocal Translocation ◽  
Cytological Study ◽  
B Chromosomes ◽  
The Other ◽  
Meiotic Pairing ◽  
Structural Hybridity ◽  
Supernumerary Chromosomes

Cytological study of a diploid (2n = 12) population of Tradescantia hirsuticaulis Small from Stone Mountain, Georgia, revealed striking variation in four plants growing in a cluster, indicating that they constitute different genotypes. The occurrence of B chromosomes, fragments, and aneusomaty in the plants is associated with structural hybridity in the chromosomes. Two plants were homozygotes with simple meiotic pairing, one was heterozygous for a reciprocal translocation, and the other was a heterozygote for two interchanges as well as for inversions. The behavior and the origin of B chromosomes, fragments, and structural hybridity are discussed.

Undertransmission of a supernumerary chromosome segment through heterozygous females possessing B chromosomes in the grasshopper Eyprepocnemis plorans

Genome ◽  
1994 ◽  
Vol 37 (4) ◽  
pp. 705-709 ◽  
Author(s):  
M. D. López-León ◽  
M. C. Pardo ◽  
J. Cabrero ◽  
J. P. M. Camacho
Keyword(s):  
Extra Chromosome ◽  
Natural Populations ◽  
Supernumerary Chromosome ◽  
B Chromosomes ◽  
Chromosome Segment ◽  
Transmission Ratio ◽  
Eyprepocnemis Plorans ◽  
Mendelian Transmission

The transmission ratio (ks) for a supernumerary chromosome segment was studied in a total of 54 heterozygous females collected from two Spanish natural populations of the grasshopper Eyprepocnemis plorans. Our analysis clearly demonstrated that ks is negatively dependent on the number of B chromosomes in the female. The possible mechanisms by which B chromosomes may cause undertransmission of the supernumerary segment, and the implications of this phenomenon for the maintenance of this extra chromosome segment, are discussed.Key words: supernumerary segments, B chromosomes, Mendelian transmission, grasshoppers.

The number and distribution of incompatibility factors in natural populations of Pleurotus ostreatus and Pleurotus sapidus

1991 ◽  
Vol 69 (10) ◽  
pp. 2187-2191 ◽  
Author(s):  
Neil A. Anderson ◽  
Glenn R. Furnier ◽  
Andrew S. Wang ◽  
John W. Schwandt
Keyword(s):  
Population Genetics ◽  
Mating System ◽  
Key Words ◽  
Pleurotus Ostreatus ◽  
Small Area ◽  
Spatial Clustering ◽  
Natural Populations ◽  
Single Spore ◽  
Single Tree ◽  
Pleurotus Sapidus

Pairings of single-spore isolates from different basidiocarps were made to examine the numbers and distributions of incompatibility factors in the tetrapolar basidiomycetes Pleurotus ostreatus and Pleurotus sapidus. These factors do not appear to be randomly distributed, with multiple basidiocarps on a single tree or log arising from a single mycelium, multiple basidiocarps on a single tree or log sharing a single common monokaryotic parent, and a tendency toward spatial clustering of factors even when multiple basidiocarps from the same tree or log are excluded from the analyses. For one 30-km2 collection area, the estimated numbers of A and B factors in the P. ostreatus population were 126 and 354, respectively, yielding an estimated outbreeding efficiency of 0.99. Estimated outbreeding efficiencies were quite high [Formula: see text] even in a sample taken from a very small area (0.09 m2), illustrating the ability of the tetrapolar mating system to simultaneously prevent self mating and minimize the number of incompatible matings. Key words: Basidiomycotina, fungi, mating system, population genetics.

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