Incorporation of a dideoxy analog prevents further elongation and so produces a chain termination extension product.
双脱氧类似物的插入将阻止进一步延伸，而产生链终止延伸产物。
英语百科
Chain termination
Chain termination is any chemical reaction that ceases the formation of reactive intermediates in a chain propagation step in the course of a polymerization, effectively bringing it to a halt.
Chemical reaction in which a chain carrier is converted irreversibly into a non-propagating species, without the formation of a new chain carrier.