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Open Access Research article

A comparative physical map reveals the pattern of chromosomal evolution between the turkey (Meleagris gallopavo) and chicken (Gallus gallus) genomes

Yang Zhang1, Xiaojun Zhang1, Thomas H O'Hare2, William S Payne3, Jennifer J Dong1, Chantel F Scheuring1, Meiping Zhang1, James J Huang1, Mi-Kyung Lee1, Mary E Delany2*, Hong-Bin Zhang1* and Jerry B Dodgson3*

Author Affiliations

1 Department of Soil and Crop Sciences, Texas A&M University, College Station, TX 77843, USA

2 Department of Animal Science, University of California, Davis, CA 95616, USA

3 Department of Microbiology & Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA

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BMC Genomics 2011, 12:447  doi:10.1186/1471-2164-12-447

Published: 9 September 2011

Abstract

Background

A robust bacterial artificial chromosome (BAC)-based physical map is essential for many aspects of genomics research, including an understanding of chromosome evolution, high-resolution genome mapping, marker-assisted breeding, positional cloning of genes, and quantitative trait analysis. To facilitate turkey genetics research and better understand avian genome evolution, a BAC-based integrated physical, genetic, and comparative map was developed for this important agricultural species.

Results

The turkey genome physical map was constructed based on 74,013 BAC fingerprints (11.9 × coverage) from two independent libraries, and it was integrated with the turkey genetic map and chicken genome sequence using over 41,400 BAC assignments identified by 3,499 overgo hybridization probes along with > 43,000 BAC end sequences. The physical-comparative map consists of 74 BAC contigs, with an average contig size of 13.6 Mb. All but four of the turkey chromosomes were spanned on this map by three or fewer contigs, with 14 chromosomes spanned by a single contig and nine chromosomes spanned by two contigs. This map predicts 20 to 27 major rearrangements distinguishing turkey and chicken chromosomes, despite up to 40 million years of separate evolution between the two species. These data elucidate the chromosomal evolutionary pattern within the Phasianidae that led to the modern turkey and chicken karyotypes. The predominant rearrangement mode involves intra-chromosomal inversions, and there is a clear bias for these to result in centromere locations at or near telomeres in turkey chromosomes, in comparison to interstitial centromeres in the orthologous chicken chromosomes.

Conclusion

The BAC-based turkey-chicken comparative map provides novel insights into the evolution of avian genomes, a framework for assembly of turkey whole genome shotgun sequencing data, and tools for enhanced genetic improvement of these important agricultural and model species.