Abstract
Individual chromosome arms have specific individual telomere lengths (TLs). Past studies within species have shown strong positive correlations between individual chromosome length and TL at that chromosome. While the reasons for these associations are unclear, the strength and consistency of the associations across disparate taxa suggest that this is important to telomere biology and should be explored further. If TL is primarily determined by chromosome length, then chromosome length should be considered and controlled for in cross-species analyses of TL. Here, we employ a cross-species approach to explore whether the chromosome length–TL association observed intraspecifically is a determinant of mean TL across species. Data were compiled from two studies characterizing TL across a range of mammalian taxa and analysed in a phylogenetic framework. We found no significant relationship between TL and chromosome size across mammals or within mammalians orders. The pattern trends in the expected direction and we suggest may be masked by evolutionary lag effects.
Highlights
Telomeres are a repetitive nucleotide sequence that cap the ends of linear chromosomes in eukaryotic organisms and protect chromosome ends from degradation due to incomplete end replication [1]
No phylogenetic signal for mean chromosome size was detected within orders (λ = 0.0000001), but a strong phylogenetic signal is observed across all analysed mammalian taxa once the outlier, Muntiacus muntjak, was removed (λ = 0.79; table 1)
The removal of the Indian muntjac from the largest dataset increased the magnitude of the positive relationship and decreased the p-value from 0.65 to 0.16. Both the large impact of this single outlier and the overall low power to detect a significant relationship (7–27% across analyses) suggest that sample size is a primary factor contributing to these null results
Summary
Telomeres are a repetitive nucleotide sequence that cap the ends of linear chromosomes in eukaryotic organisms and protect chromosome ends from degradation due to incomplete end replication [1]. Only mean TL is typically measured, despite the fact that every individual chromosome end has a characteristic TL [3,4,5]. The fine-scale specificity of TL at the level of chromosome arms suggests a great deal of telomere biology and patterns of variation in TL could be masked by only considering mean TL. Hinting at important TL dynamics, 2018 The Authors.
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