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

被称为“甲基原”学实体附着DNA片段上，这会对哪些序列活跃产生影响。

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

我们知道某些原特定方式下具有特定功能。

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

这里，原会与原来舞伴告别， 因为它们交联断裂了。

Then the groups pair up to crosslink with new partners.

然后这些原会重新配对， 与新舞伴形成交联。