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

被称为“甲基原子”的小化学实体附着在DNA片段上，这会对哪些列是活跃的产生影响。

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的长链。

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

在这里，原子在它们的交联断裂时向它们的伙伴说再见。

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

这种固化会在这种塑料的原子之间形交联。