Small chemical entities called methyl groups attach to stretches of DNA, which affects what sequences are active.

被称为“甲基原子团”的小体附着在DNA片段上，会对哪些列是活跃的产生影响。

That curing forms crosslinks among groups of atoms in this plastic.

种固会在种塑料的原子团之间形成交联。

Their molecules are basically long chains of repeating groups of atoms.

它们的分子基本上是由重复的原子团组成的长链。

Here, groups of atoms say goodbye to their partners as their crosslinks break apart.

在里，原子团在它们的交联断裂时向它们的伙伴说再见。