TDG (Thymine-DNA glycosylase)

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Human Uniqueness Compared to "Great Apes": 
Likely Difference
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Thymine-DNA Gycosylase (TDG) is a DNA repair enzyme that is responsible for removing thymine from G/T mismatches and as such is an important part of cellular defense against genetic mutations. In addition to its primary function, TDG can also repair other types of mismatches at a lower affinity and has been shown to interact with multiple transcription factors and be involved in demethylation, which implicate it in gene regulation. Array comparative genomic hybridization indicates that CDH12 is present in the human genome in higher copy number than any other primate, however, the significance of this change in copy number is unknown.


Timing of appearance of the difference in the Hominin Lineage as a defined date or a lineage separation event. The point in time associated with lineage separation events may change in the future as the scientific community agrees upon better time estimates. Lineage separation events are defined in 2017 as:

  • the Last Common Ancestor (LCA) of humans and old world monkeys was 25,000 - 30,000 thousand (25 - 30 million) years ago
  • the Last Common Ancestor (LCA) of humans and chimpanzees was 6,000 - 8,000 thousand (6 - 8 million) years ago
  • the emergence of the genus Homo was 2,000 thousand (2 million) years ago
  • the Last Common Ancestor (LCA) of humans and neanderthals was 500 thousand years ago
  • the common ancestor of modern humans was 100 - 300 thousand years ago

Definite Appearance: 
6,000 thousand years ago
Genetics Topic Attributes
Gene symbols follow the HUGO Gene Nomenclature Committee standard.
Gene Symbol Type of Human-Specific Changes
TDG Copy Number Changes


  1. Identification of human specific gene duplications relative to other primates by array CGH and quantitative PCR., Armengol, Gemma, Knuutila Sakari, Lozano Juan-José, Madrigal Irene, and Caballín María-Rosa , Genomics, 2010 Apr, Volume 95, Issue 4, p.203-9, (2010)
  2. The enigmatic thymine DNA glycosylase., Cortázar, Daniel, Kunz Christophe, Saito Yusuke, Steinacher Roland, and Schär Primo , DNA Repair (Amst), 2007 Apr 1, Volume 6, Issue 4, p.489-504, (2007)
  3. 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)