These DNA units, known as telomeres, act like the plastic caps at the ends of a shoelace, keeping the chromosomes from fraying and the genes inside them from unraveling.

• 这些DNA部分即所谓的端粒，它们的作用类似鞋带两头的塑料帽，可以保持染色体不会磨损，里面的基因不会散开。