Telomeres are special structures at the ends of chromosomes, especially in eukaryotes, that include repetitive sequences of deoxyribonucleic acid (DNA) and non-nucleosomal proteins. These structures are essential to protect chromosomes from recombination and degradation. Telomeres are gene-poor repetitive sequences, but they are close to the more gene-rich subtelomeric regions. Proteins associated with telomeres are able to interact directly with the TTAGGG repeats and also can bind to other factors to form large protein complexes. These proteins are involved in DNA repair and telomere stability. Therefore, defects in the synthesis of these proteins could induce imperfections in telomere maintenance and DNA repair; and accordingly, should cause a number of genetic syndromes. Keywords: Telomere, DNA damage, Genetic diseases