B chromosome

A small B chromosome in the grasshopper Ommexecha virens (Ommexechidae)

T. E. Souza, Silva-Neto, L. C., Santos, J. F., Loreto, V., and Rieger, T. T., A small B chromosome in the grasshopper Ommexecha virens (Ommexechidae), vol. 14. pp. 17505-17510, 2015.

B chromosomes, also called supernumerary or accessory chromosomes, have been characterized as extra elements found in the karyotypes of different eukaryotic species. B chromosomes are nonvital and only occur in some individuals within a species. Moreover, the chromosomes contain silenced genes, and they exhibit heterochromatinization and the accumulation of repetitive DNA and transposons.

Meiotic pairing of B chromosomes, multiple sexual system, and Robertsonian fusion in the red brocket deer Mazama americana (Mammalia, Cervidae)

C. I. Aquino, Abril, V. V., and Duarte, J. M. B., Meiotic pairing of B chromosomes, multiple sexual system, and Robertsonian fusion in the red brocket deer Mazama americana (Mammalia, Cervidae), vol. 12, pp. 3566-3574, 2013.

Deer species of the genus Mazama show significant inter- and intraspecific chromosomal variation due to the occurrence of rearrangements and B chromosomes. Given that carriers of aneuploidies and structural rearrangements often show anomalous chromosome pairings, we here performed a synaptonemal complex analysis to study chromosome pairing behavior in a red brocket deer (Mazama americana) individual that is heterozygous for a Robertsonian translocation, is a B chromosome carrier, and has a multiple sex chromosome system (XY1Y2).

Karyotype description of two species of Hypostomus (Siluriformes, Loricariidae) of the Planalto da Bodoquena, Brazil

S. S. Cereali, Pomini, E., Rosa, R., Zawadzki, C. H., Froehlich, O., and Giuliano-Caetano, L., Karyotype description of two species of Hypostomus (Siluriformes, Loricariidae) of the Planalto da Bodoquena, Brazil, vol. 7, pp. 583-591, 2008.

Hypostomus sp 3-Córrego Salobrinha NUP 4247 and Hypostomus sp 2-Rio Perdido NUP 4249, collected in the Planalto da Bodoquena, Paraguay River basin, Brazil, were characterized cytogenetically. Hypostomus sp 3-Córrego Salobrinha showed two modal numbers. This polymorphism consists of the presence of two extrachromosomes. It was not possible to define the diploid number in four specimens, where cell lineages had 2n = 83 and 2n = 84 chromosomes in one individual, and 2n = 82, 2n = 83 and 2n = 84 chromosomes in the others.

B chromosomes in popcorn (Zea mays L.)

G. L. Ricci, Silva, N., Pagliarini, M. S., and Scapim, C. A., B chromosomes in popcorn (Zea mays L.), vol. 6, pp. 137-143, 2007.

Cytological analysis of microsporogenesis in 72 popcorn plants, comprising nine from the original population (CMS-43, S0) and 63 from seven cycles of self-fertilization (S1 to S7), one plant of S0 generation (plant 2) was identified with B chromosomes. The number of B chromosomes varied from two to three in the same anther. The pattern of chromosome pairing and meiotic behavior of Bs were similar to those found in other plant species. The presence of B chromosomes did not affect chiasma frequency and chiasma distribution in A chromosomes.

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