Task: Text Categorization
Input (English): They often form stacks of G-quadruplexes with potassium or sodium ions between each quadruplex. They are not necessary or present in most prokaryotes, especially those with circular DNA, and are only maintained in the germ cells of multicellular eukaryotes. When they become uncapped, they can lead to apoptosis or senescence of somatic cells, which may be the root of normal aging. Considered the solution to Watson's "end-replication problem," FTP, identify these repeated nucleotide sequences that protect and define the ends of chromosomes.
Output (English): Science