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01 / 03 · Chromosome ends
Chromosome ends: where telomeres sit
Telomeres are protective DNA–protein structures at the ends of linear chromosomes. This overview locates the ends before we look more closely at telomeric DNA and telomerase.
This replicated chromosome has two sister chromatids, each with two ends: four telomere locations in total. Select the chromosome or its gold-highlighted ends.
Start at the chromosome ends
The highlighted tips mark where telomeres are located. Continue to see the repeated DNA sequence and a structural model of telomeric DNA.
Simplified replicated metaphase chromosome schematic, not to scale. Telomeres are also present when chromosomes are uncondensed; the illustration is not an experimental structure.
Methods & sources
Experimental coordinates are kept fixed. Rotation and zoom change the view; they do not simulate molecular motion, docking or enzyme activity. The different views use independent scales.
Chromosome-end overview: original schematic of a replicated metaphase chromosome, with four highlighted ends: two per sister chromatid. An unreplicated chromosome has two ends. Gold indicates location, not length; the model is not to scale. The guide then turns to experimental structures of telomeric DNA and the telomerase catalytic core. Background: de Lange (2018), Shelterin-mediated telomere protection.
Telomeric DNA: PDB 2JSL, deposited NMR model 1, 25 nucleotides. Hydrogen atoms are hidden; no potassium positions are added. Phan et al. (2007).
Human telomere repeat: telomerase synthesizes the TTAGGG repeat at chromosome ends. Morin (1989).
Telomerase: PDB 7BG9, human catalytic core, cryo-EM at 3.8 Å. Chain A: TERT; chain B: TERC; chain N: synthetic 18-nucleotide DNA substrate (5′-TTTTTTTTTTTTTTAGGG-3′); chains L/M: H2A/H2B. Unresolved regions and the rest of the holoenzyme are not reconstructed. Ghanim et al. (2021).
Models prepared in Blender with Molecular Nodes; displayed with Three.js. Colours identify components, not chemical elements. Structural provenance · Software licence.