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DNA repeat arrays in chicken and human genomes and the adaptive evolution of avian genome size
BACKGROUND: Birds have smaller average genome sizes than other tetrapod classes, and it has been proposed that a relatively low frequency of repeating DNA is one factor in reduction of avian genome sizes. RESULTS: DNA repeat arrays in the sequenced portion of the chicken (Gallus gallus) autosomes we...
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Formato: | Texto |
Lenguaje: | English |
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BioMed Central
2005
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC548695/ https://www.ncbi.nlm.nih.gov/pubmed/15694002 http://dx.doi.org/10.1186/1471-2148-5-12 |
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author | Hughes, Austin L Piontkivska, Helen |
author_facet | Hughes, Austin L Piontkivska, Helen |
author_sort | Hughes, Austin L |
collection | PubMed |
description | BACKGROUND: Birds have smaller average genome sizes than other tetrapod classes, and it has been proposed that a relatively low frequency of repeating DNA is one factor in reduction of avian genome sizes. RESULTS: DNA repeat arrays in the sequenced portion of the chicken (Gallus gallus) autosomes were quantified and compared with those in human autosomes. In the chicken 10.3% of the genome was occupied by DNA repeats, in contrast to 44.9% in human. In the chicken, the percentage of a chromosome occupied by repeats was positively correlated with chromosome length, but even the largest chicken chromosomes had repeat densities much lower than those in human, indicating that avoidance of repeats in the chicken is not confined to minichromosomes. When 294 simple sequence repeat types shared between chicken and human genomes were compared, mean repeat array length and maximum repeat array length were significantly lower in the chicken than in human. CONCLUSIONS: The fact that the chicken simple sequence repeat arrays were consistently smaller than arrays of the same type in human is evidence that the reduction in repeat array length in the chicken has involved numerous independent evolutionary events. This implies that reduction of DNA repeats in birds is the result of adaptive evolution. Reduction of DNA repeats on minichromosomes may be an adaptation to permit chiasma formation and alignment of small chromosomes. However, the fact that repeat array lengths are consistently reduced on the largest chicken chromosomes supports the hypothesis that other selective factors are at work, presumably related to the reduction of cell size and consequent advantages for the energetic demands of flight. |
format | Text |
id | pubmed-548695 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2005 |
publisher | BioMed Central |
record_format | MEDLINE/PubMed |
spelling | pubmed-5486952005-02-13 DNA repeat arrays in chicken and human genomes and the adaptive evolution of avian genome size Hughes, Austin L Piontkivska, Helen BMC Evol Biol Research Article BACKGROUND: Birds have smaller average genome sizes than other tetrapod classes, and it has been proposed that a relatively low frequency of repeating DNA is one factor in reduction of avian genome sizes. RESULTS: DNA repeat arrays in the sequenced portion of the chicken (Gallus gallus) autosomes were quantified and compared with those in human autosomes. In the chicken 10.3% of the genome was occupied by DNA repeats, in contrast to 44.9% in human. In the chicken, the percentage of a chromosome occupied by repeats was positively correlated with chromosome length, but even the largest chicken chromosomes had repeat densities much lower than those in human, indicating that avoidance of repeats in the chicken is not confined to minichromosomes. When 294 simple sequence repeat types shared between chicken and human genomes were compared, mean repeat array length and maximum repeat array length were significantly lower in the chicken than in human. CONCLUSIONS: The fact that the chicken simple sequence repeat arrays were consistently smaller than arrays of the same type in human is evidence that the reduction in repeat array length in the chicken has involved numerous independent evolutionary events. This implies that reduction of DNA repeats in birds is the result of adaptive evolution. Reduction of DNA repeats on minichromosomes may be an adaptation to permit chiasma formation and alignment of small chromosomes. However, the fact that repeat array lengths are consistently reduced on the largest chicken chromosomes supports the hypothesis that other selective factors are at work, presumably related to the reduction of cell size and consequent advantages for the energetic demands of flight. BioMed Central 2005-02-04 /pmc/articles/PMC548695/ /pubmed/15694002 http://dx.doi.org/10.1186/1471-2148-5-12 Text en Copyright © 2005 Hughes and Piontkivska; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( (http://creativecommons.org/licenses/by/2.0) ), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Research Article Hughes, Austin L Piontkivska, Helen DNA repeat arrays in chicken and human genomes and the adaptive evolution of avian genome size |
title | DNA repeat arrays in chicken and human genomes and the adaptive evolution of avian genome size |
title_full | DNA repeat arrays in chicken and human genomes and the adaptive evolution of avian genome size |
title_fullStr | DNA repeat arrays in chicken and human genomes and the adaptive evolution of avian genome size |
title_full_unstemmed | DNA repeat arrays in chicken and human genomes and the adaptive evolution of avian genome size |
title_short | DNA repeat arrays in chicken and human genomes and the adaptive evolution of avian genome size |
title_sort | dna repeat arrays in chicken and human genomes and the adaptive evolution of avian genome size |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC548695/ https://www.ncbi.nlm.nih.gov/pubmed/15694002 http://dx.doi.org/10.1186/1471-2148-5-12 |
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