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Genes 2018, 9(10), 487;

B Chromosomes in Populations of Mammals Revisited

Institute for Biological Research “Siniša Stanković”, Department of Genetic Research, University of Belgrade, Bulevar despota Stefana 142, Belgrade 11060, Serbia
Author to whom correspondence should be addressed.
Received: 29 August 2018 / Revised: 1 October 2018 / Accepted: 3 October 2018 / Published: 9 October 2018
(This article belongs to the Special Issue Evolution, Composition and Regulation of Supernumerary B Chromosomes)
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The study of B chromosomes (Bs) started more than a century ago, while their presence in mammals dates since 1965. As the past two decades have seen huge progress in application of molecular techniques, we decided to throw a glance on new data on Bs in mammals and to review them. We listed 85 mammals with Bs that make 1.94% of karyotypically studied species. Contrary to general view, a typical B chromosome in mammals appears both as sub- or metacentric that is the same size as small chromosomes of standard complement. Both karyotypically stable and unstable species possess Bs. The presence of Bs in certain species influences the cell division, the degree of recombination, the development, a number of quantitative characteristics, the host-parasite interactions and their behaviour. There is at least some data on molecular structure of Bs recorded in nearly a quarter of species. Nevertheless, a more detailed molecular composition of Bs presently known for six mammalian species, confirms the presence of protein coding genes, and the transcriptional activity for some of them. Therefore, the idea that Bs are inert is outdated, but the role of Bs is yet to be determined. The maintenance of Bs is obviously not the same for all species, so the current models must be adapted while bearing in mind that Bs are not inactive as it was once thought. View Full-Text
Keywords: supernumerary chromosomes; additional chromosomes; chromosome polymorphism; evolution supernumerary chromosomes; additional chromosomes; chromosome polymorphism; evolution
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Vujošević, M.; Rajičić, M.; Blagojević, J. B Chromosomes in Populations of Mammals Revisited. Genes 2018, 9, 487.

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