Telomere and Subtelomere Changes

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True   Likely   Speculative
Human Uniqueness Compared to "Great Apes": 
Likely Difference
MOCA Domain: 

Telomeres are repetitive sequences of DNA at the ends of chromosomes that protect the chromosomes from degradation and allow for chromosomal shortening during replication while maintaining gene integrity at the end of the chromosome. Human telomeres, with the exception of those in human sperm, are much shorter than telomeres in non-human primates. While human telomeres are shorter overall, there are gene families within telomeric regions, such as the KIR family, that have undergone human lineage specific duplication, have unique locations in telomeres in humans, and have undergone recombination and conversion events. Subtelomeric regions lie adjacent to telomeres and contain similar genetic content to that of pericentromeric regions, including segmental duplications and bands of heterochromatin. The source of subtelomeric duplication sequences is primarily from other subtelomeric regions, and in contrast to telomere shortening, subtelomeric sequences have undergone human-specific large-scale duplication events since the Homo-Pan split. These regions are therefore major sites housing genes that have undergone human lineage-specific copy number increases and contain sequences that have dispersed in a human-specific fashion to novel regions of the genome, an example being the sequence f7501 that has a single copy in non-human primates and 7-11 copies in humans at subtelomeric locations on multiple chromosomes.

The Human Difference: 

Length difference
Copy number variation
Gene conversion

References

  1. Different patterns of evolution in the centromeric and telomeric regions of group A and B haplotypes of the human killer cell Ig-like receptor locus., Pyo, Chul-Woo, Guethlein Lisbeth A., Vu Quyen, Wang Ruihan, Abi-Rached Laurent, Norman Paul J., Marsh Steven G. E., Miller Jeffrey S., Parham Peter, and Geraghty Daniel E. , PLoS One, 2010, Volume 5, Issue 12, p.e15115, (2010)
  2. Primate segmental duplications: crucibles of evolution, diversity and disease., Bailey, Jeffrey A., and Eichler Evan E. , Nat Rev Genet, 2006 Jul, Volume 7, Issue 7, p.552-64, (2006)
  3. The dynamic nature and evolutionary history of subtelomeric and pericentromeric regions., Mewborn, S K., C Martin Lese, and Ledbetter D H. , Cytogenet Genome Res, 2005, Volume 108, Issue 1-3, p.22-5, (2005)
  4. Lineage-specific gene duplication and loss in human and great ape evolution., Fortna, A., Kim Y., MacLaren E., Marshall K., Hahn G., Meltesen L., Brenton M., Hink R., Burgers S., Hernandez-Boussard T., et al. , PLoS Biol, 07/2004, Volume 2, Issue 7, p.E207, (2004)
  5. The complex structure and dynamic evolution of human subtelomeres., Mefford, Heather C., and Trask Barbara J. , Nat Rev Genet, 2002 Feb, Volume 3, Issue 2, p.91-102, (2002)
  6. The evolutionary origin of human subtelomeric homologies--or where the ends begin., Martin, Christa Lese, Wong Andrew, Gross Alyssa, Chung June, Fantes Judy A., and Ledbetter David H. , Am J Hum Genet, 2002 Apr, Volume 70, Issue 4, p.972-84, (2002)
  7. Human is a unique species among primates in terms of telomere length., Kakuo, S, Asaoka K, and Ide T , Biochem Biophys Res Commun, 1999 Sep 24, Volume 263, Issue 2, p.308-14, (1999)
  8. Recent human-specific spreading of a subtelomeric domain., Monfouilloux, S, Avet-Loiseau H, Amarger V, Balazs I, Pourcel C, and Vergnaud G , Genomics, 1998 Jul 15, Volume 51, Issue 2, p.165-76, (1998)