Origin of B chromosomes in Characidium alipioi (Characiformes, Crenuchidae) and its relationship with supernumerary chromosomes in other Characidium species

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.

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Structural hybridity and supernumerary chromosomes in a diploid Tradescantia hirsuticaulis

Canadian Journal of Botany ◽

10.1139/b75-056 ◽

1975 ◽

Vol 53 (5) ◽

pp. 456-465 ◽

Cited By ~ 2

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.

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

Genome ◽

10.1139/g87-002 ◽

1987 ◽

Vol 29 (1) ◽

pp. 5-10 ◽

Cited By ~ 8

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.

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Molecular analysis of Drosophila melanogaster B chromosomes reveals their origin, composition, and structure

10.1101/386995 ◽

2018 ◽

Author(s):

Stacey L. Hanlon ◽

Danny E. Miller ◽

Salam Eche ◽

R. Scott Hawley

Keyword(s):

Drosophila Melanogaster ◽

Molecular Analysis ◽

Model Organism ◽

B Chromosome ◽

B Chromosomes ◽

Individual Species ◽

Satellite Repeat ◽

Supernumerary Chromosomes ◽

Laboratory Stock ◽

Composition And Structure

ABSTRACTThe number of chromosomes carried by an individual species is one of its defining characteristics. Some species, however, can also carry supernumerary chromosomes referred to as B chromosomes. B chromosomes were recently identified in a laboratory stock of Drosophila melanogaster—an established model organism with a wealth of genetic and genomic resources—enabling us to subject them to extensive molecular analysis. We isolated the B chromosomes by pulsed-field gel electrophoresis and determined their composition through next-generation sequencing. Although these B chromosomes carry no known euchromatic sequence, they are rich in transposable elements and long arrays of short nucleotide repeats, the most abundant being the uncharacterized AAGAT satellite repeat. Fluorescent in-situ hybridization on metaphase chromosome spreads revealed this repeat is located on Chromosome 4, strongly suggesting the origin of the B chromosomes is Chromosome 4. Cytological and quantitative comparisons of signal intensity between Chromosome 4 and the B chromosomes supports the hypothesis that the structure of the B chromosome is an isochromosome. We also report the identification of a new B chromosome variant in a related laboratory stock. This B chromosome has a similar repeat signature as the original but is smaller and much less prevalent. We examined additional stocks with similar genotypes and did not find B chromosomes, but did find these stocks lacked the AAGAT satellite repeat. Our molecular characterization of D. melanogaster B chromosomes is the first step towards understanding how supernumerary chromosomes arise from essential chromosomes and what may be necessary for their stable inheritance.

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

International Journal of Molecular Sciences ◽

10.3390/ijms222413617 ◽

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.

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The B Chromosomes of Prochilodus lineatus (Teleostei, Characiformes) Are Highly Enriched in Satellite DNAs

Cells ◽

10.3390/cells10061527 ◽

2021 ◽

Vol 10 (6) ◽

pp. 1527

Author(s):

José Henrique Forte Stornioli ◽

Caio Augusto Gomes Goes ◽

Rodrigo Milan Calegari ◽

Rodrigo Zeni dos Santos ◽

Leonardo Moura Giglio ◽

...

Keyword(s):

Repetitive Dna ◽

Fish Species ◽

Satellite Dna ◽

B Chromosomes ◽

Entire Population ◽

Satellite Dnas ◽

Prochilodus Lineatus ◽

Supernumerary Chromosomes ◽

Morphological Variants ◽

First Time

B or supernumerary chromosomes are dispensable elements that are widely present in numerous eukaryotes. Due to their non-recombining nature, there is an evident tendency for repetitive DNA accumulation in these elements. Thus, satellite DNA plays an important role in the evolution and diversification of B chromosomes and can provide clues regarding their origin. The characiform Prochilodus lineatus was one of the first discovered fish species bearing B chromosomes, with all populations analyzed so far showing one to nine micro-B chromosomes and exhibiting at least three morphological variants (Ba, Bsm, and Bm). To date, a single satellite DNA is known to be located on the B chromosomes of this species, but no information regarding the differentiation of the proposed B-types is available. Here, we characterized the satellitome of P. lineatus and mapped 35 satellite DNAs against the chromosomes of P. lineatus, of which six were equally located on all B-types and this indicates a similar genomic content. In addition, we describe, for the first time, an entire population without B chromosomes.

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Karyological study of cicindelidia trifasciata (coleoptera, cicindelidae) from cuba: evidence of B chromosomes

Genetics and Molecular Biology ◽

10.1590/s1415-47571999000100010 ◽

1999 ◽

Vol 22 (1) ◽

pp. 45-48 ◽

Cited By ~ 4

Author(s):

Sónia J.R. Proença ◽

M.J. Collares-Pereira ◽

A.R.M. Serrano

Keyword(s):

Sex Chromosome ◽

B Chromosome ◽

B Chromosomes ◽

Karyological Study ◽

Supernumerary Chromosomes ◽

Sex Chromosome System ◽

Well Differentiated ◽

Germinal Tissue

Metaphases from germinal tissue of eight males and seven females of Cicindelidia trifasciata from Cuba were analyzed. The species karyotype does not fit the pattern described for Nearctic cicindelids (2n = 18 + XXY): it has 11 autosome pairs and a sex chromosome system of the X1X2X3Y/ X1X1X2X2 X3X3 type, thus a diploid value of 2n = 26 in males and 2n = 28 in females. The first two autosome pairs were almost twice as large as the remaining chromosomes, and the sex elements were morphologically well differentiated. This population was found to be polymorphic for supernumerary chromosomes at both the intraindividual and interindividual levels. An extra small B chromosome was observed in all metaphases of one male (2n = 27), and every female showed metaphases with one to three small Bs, with a clearly higher frequency of cytotype 2n = 29.

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Multiple supernumerary chromosomes in the pseudogamous parthenogenetic flatworm Polycelis nigra: lineage markers or remnants of genetic leakage?

Genome ◽

10.1139/g97-810 ◽

1997 ◽

Vol 40 (6) ◽

pp. 850-856 ◽

Cited By ~ 3

Author(s):

Timothy F. Sharbel ◽

Leo W. Beukeboom ◽

Laas P. Pijnacker

Keyword(s):

Chromosome Doubling ◽

B Chromosome ◽

B Chromosomes ◽

Banding Technique ◽

Free Living ◽

Transmission Rates ◽

Supernumerary Chromosomes ◽

C Banding ◽

Male Line ◽

Lineage Markers

Polycelis nigra is a free-living simultaneous hermaphroditic flatworm that has amphimictic and pseudogamous parthenogenetic biotypes. Sexual individuals are always diploid (2n = 16) and pseudogamous parthenogens are polyploid (usually triploid). Two types of supernumerary chromosomes are found in parthenogens, those resembling autosomes ("A-like") and typical B chromosomes, both of which reach frequencies in populations of close to 100%. Experiments measuring the transmission rates of the B chromosomes indicated that they are potentially inherited via the male line, escaping expulsion by pseudogamous parthenogenesis. This study used the C-banding technique to demonstrate (i) that there is a single morphologically distinct B chromosome (B1) and (ii) that there are two "A-like" chromosomes that can be considered B chromosomes (B2 and B3) and which are not simple polysomics of one of the eight autosomes. As there is no genetic exchange between pseudogamous parthenogenetic lineages, two different individuals carrying a similar B morph must either have received it through common ancestry (a lineage marker) or have acquired it horizontally from another parthenogenetic lineage (leakage). C-banding further revealed intra-individual heteromorphy for band regions on chromosomes 5 and 8. This supports the karyotypic observation that oogenesis is preceded by premeiotic chromosome doubling followed by pairing of replicate homologues.Key words: B chromosome, C-banding, heterochromatin, heteromorphy, pseudogamous parthenogenesis.

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

Genome ◽

10.1139/g87-004 ◽

1987 ◽

Vol 29 (1) ◽

pp. 19-25 ◽

Cited By ~ 2

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.

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B Chromosome Diversity and Repetitive Sequence Distribution in an Isolated Population of Akodon montensis (Rodentia, Sigmodontinae)

Cytogenetic and Genome Research ◽

10.1159/000487471 ◽

2018 ◽

Vol 154 (2) ◽

pp. 79-85

Author(s):

Amanda A. Soares ◽

Jonathan P. Castro ◽

Pedro Balieiro ◽

Sidnei Dornelles ◽

Tiago M. Degrandi ◽

...

Keyword(s):

Evolutionary Dynamics ◽

Repetitive Sequences ◽

5S Rdna ◽

B Chromosome ◽

B Chromosomes ◽

Telomeric Sequences ◽

Supernumerary Chromosomes ◽

Dna Libraries ◽

Eukaryotic Species ◽

Size And Morphology

B chromosomes are supernumerary chromosomes found in the karyotypes of approximately 15% of all eukaryotic species. They present parasitic behavior and do not follow the standard Mendelian pattern of inheritance, resulting in an imbalance in gametogenesis. The evolutionary dynamics of B chromosomes is still unknown for many species, but studies indicate that the accumulation of repetitive sequences plays an important role in the differentiation of these elements. We analyzed morphology, frequency, and possible homologies amongst different B chromosomes found in an isolated Akodon montensis population in southern Brazil. Repetitive sequences (18S, 5S rDNA and telomeric sequences) were used to test for their accumulation on the supernumerary chromosomes and describe their localization in the species. The results indicate 4 different B chromosome morphotypes, and DNA libraries were generated for 3 of them. 18S rDNA was labelled polymorphically, except in the B chromosomes, whereas the 5S rDNA was located exclusively in an interstitial position on the long arm of chromosome 5. Chromosome painting with the B probes based on FISH revealed a homologous composition for all B chromosome morphotypes and no homology with the chromosomes in the A complement. B chromosomes found in this population may have a common origin and subsequently diversified in size and morphology.

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