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”的小化实体附着DNA片段上，会对哪些序列活跃的产生影响。

And we know that certain groups of bonded atoms function in very specific ways.

我们知道某些原子团特定的方式下具有特定的功能。

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

里，原子团会与原来的舞伴告别， 因为它们的交联断裂了。

Then the groups pair up to crosslink with new partners.

然后些原子团会重新配对， 与新的舞伴形成交联。