B chromosome

From Wikipedia, the free encyclopedia

B chromosomes are small supernumerary chromosomes found in many eukaryotic nuclei that are believed to be largely non-coding and probably parasitic on the host genome.

B chromosomes play an important role on normal A chromosomes. The B chromosomes suppress homologous pairing which reduces multiple pairing between homologous chromosomes in allopolyploids. Bivalent pairing is ensured by a gene on chromosome 5 of the B genome Phlocus. The B chromosomes also have the following effects on A chromosomes:

increases asymmety chiasma distribution
increases crossing over and recombination frequencies: increases variation
cause increased unpaired chromosomes: infertility

B chromosomes have tendency to accumulate in meiotic cell products resulting in an increase of B number over generations. However this effect is counterbalanced for selection against infertility.

[edit] See Also

Intragenomic conflict

[edit] References

Burt, A. and R.L. Trivers (2005). Genes in Conflict: The Biology of Selfish Genetic Elements. Harvard University Press, Cambridge, MA.
Camacho J.P.M., T.F. Sharbel, and L.W. Beukeboom (2000). B-chromosome evolution. Philosophical Transactions of the Royal Society of London B 355:163-178.
Camacho, J.P.M. (ed.) (2004). B Chromosomes in the Eukaryote Genome. Special issue of Cytogenetic and Genome Research, vol. 106, nos. 2-4.
Camacho, J.P.M. (2005). B chromosomes. In The Evolution of the Genome (ed. T.R. Gregory), Elsevier, San Diego, pp. 223-286
Jones, R.N. and H. Rees (1982). B Chromosomes. Academic Press, New York.
Perfectti, F., Corral, J. M., Mesa, J. A., Cabrero, J., Bakkali, M., López-León, M. D. and Camacho. J. P. M. (2004). Rapid suppression of drive for a parasitic B chromosome. Cytogenetic and Genome Research, 106: 338-343.
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Bakkali, M. and Camacho, J. P. M. (2004). The B chromosome polymorphism of the grasshopper Eyprepocnemis plorans in northern Africa. III. Mutation rate of B chromosomes. Heredity, 92: 428-433.
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Bakkali, M., Cabrero, J. and Camacho, J. P. M. (2003). B-A interchanges are an unlikely pathway for B chromosome integration into the A genome. Chromosome Research, 11: 115-123.
Camacho, J. P. M., Cabrero, J., López-León, M. D., Bakkali, M. and Perfectti, F. (2003). The B chromosomes of the grasshopper Eyprepocnemis plorans and the intragenomic conflict. Genetica, 117: 77-84.
Camacho, J. P. M., Bakkali, M., Corral, J. M., Cabrero, J., López-León, M. D., Aranda, I., Martín-Alganza, A. and Perfectti, F. (2002). Host recombination is dependent on the degree of parasitism. Proceedings of the Royal Society of London: Biological Sciences, 269: 2173-2177.
Bakkali, M., Perfectti, F. and Camacho, J. P. M. (2002). The B-chromosome polymorphism of the grasshopper Eyprepocnemis plorans in northern Africa. II. Parasitic and neutralized B1 chromosome. Heredity, 88: 14-18.
Camacho, J. P. M., Corral, J. M., Mesa, J. A., Cabrero, J., Bakkali, M., López-León, M. D. and Perfectti, F. (2001). Neutralization of a parasitic B chromosome in the grasshopper Eyprepocnemis plorans. Chromosome Research, 9: 106.
Cabrero, J., López-León, M. D., Bakkali, M. and Camacho, J. P. M. (1999). Common origin of B chromosome variants in the grasshopper Eyprepocnemis plorans. Heredity, 83: 435-439.
Bakkali, M., Cabrero, J., López-León, M. D., Perfectti, F. and Camacho, J. P. M. (1999). The B-chromosome polymorphism of the grasshopper Eyprepocnemis plorans in northern Africa. I. B variants and frequency. Heredity, 83: 428-434.
Bakkali, M., Cabrero, J., López-León, M. D., Perfectti, F. and Camacho, J. P. M. (1998). B-chromosome polymorphism in North-African natural populations of the grasshopper Eyprepocnemis plorans. Cytogenetics and Cell Genetics, 81: 124.