期刊
CHROMOSOMA
卷 119, 期 2, 页码 217-225出版社
SPRINGER
DOI: 10.1007/s00412-009-0251-3
关键词
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资金
- Spanish Ministerio de Ciencia y Tecnologia [CGL2006-06307]
- Plan Andaluz de Investigacion [CVI-1664]
- FEDER
In addition to the standard set of chromosomes (A), about 15% of eukaryote genomes carry B chromosomes. In most cases, B chromosomes behave as genomic parasites being detrimental for the individuals carrying them and prospering in natural populations because of transmission advantages (drive). B chromosomes are mostly made up of repetitive DNA sequences, especially ribosomal DNA (rDNA), satellite DNA and mobile elements. In only two cases have B chromosomes been shown to carry protein-coding genes. Although some B chromosomes seem to have derived from interspecific hybridisation, the most likely source of B chromosomes is the host genome itself, but the specific A chromosome being the B ancestor has not been identified in any B-containing species. Here, we provide strong evidence for B chromosome ancestry in the migratory locust, based on the location of genes for the H3 and H4 histones in the B chromosome and a single A chromosome pair (i.e. the eighth in order of decreasing size). The high DNA sequence similarity of A and B chromosome H3-H4 genes supports B-origin from chromosome 8. The higher variation shown by B sequences, compared to A sequences, suggests that B chromosome sequences are most likely inactive and thus less subjected to purifying selection. Estimates of time of divergence for histone genes from A and B chromosomes suggest that B chromosomes are quite old (> 750,000 years), showing the B-chromosome ability to persist in natural populations for long periods of time.
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