TTAGGGRepeats

TTAGGGrepeats refer to a telomeric DNA motif composed of the unit TTAGG repeated in tandem at the ends of chromosomes in a subset of eukaryotes. The TTAGG unit is a five-nucleotide sequence that forms long arrays, typically located at chromosome termini where they protect chromosome ends from degradation and end-to-end fusions. This motif is especially common among many invertebrate groups, notably various insects such as Lepidoptera, and shows evolutionary variation relative to the vertebrate telomere motif TTAGGG.

In organisms carrying TTAGG repeats, telomere function is maintained by cellular mechanisms that extend or preserve these repeats. The primary maintenance system is often telomerase, a ribonucleoprotein enzyme that adds telomeric repeats to chromosome ends, though some lineages may employ alternative lengthening mechanisms in certain contexts. The structure of TTAGG telomeres supports the formation of protective telomeric ends, including the potential for G-quadruplex structures and the binding of specialized telomere-associated proteins.

Genomic and cytogenetic studies frequently use TTAGG repeats as markers. Fluorescence in situ hybridization (FISH) probes targeting TTAGG arrays enable visualization of chromosome ends and assessment of telomere length dynamics in species where this motif is present. Variation in repeat number and sequence integrity among individuals and species provides insight into telomere biology, evolution, and chromosome biology across diverse taxa.