SIRT1 depends on a molecule called NAD (Nicotinamide adenine dinucleotide), and NAD, in turn, depends on the substance called NMN.

SIRT1合成取决于一种叫NAD（辅酶）分子，而NAD合成则取决于一种叫NMN。

But for the remaining .1%, one person might have an adenine where another person has a guanine.

但对于剩下0.1%，一个人可能有嘌呤而另一个人有鸟嘌呤。

It was known that DNA had four chemical components - called adenine, guanine, cytosine, and thiamine - and that these paired up in particular ways.

当时已经知道，DNA含有4种化学成分——嘌呤、鸟嘌呤、胞啶和啶——这4种成分总是以特殊配对方式排列。

The bases - the letters of the genetic alphabet - consist of the four nucleotides mentioned a page or two back: adenine, thiamine, guanine, and cytosine.

碱基——基因子母表中字母——由前面我们提到嘌呤、鸟嘌呤、胞吟和啶4种核苷酸组成。

Nucleotides of DNA are made out of a sugar deoxyribose, a phosphate, and one of the four nuclear bases: adenine, cytosine, guanine, and thymine or A, C, G, T for short.

DNA核苷酸由脱氧核糖、磷酸以及四个核碱基之一组成，分别是嘌呤、胞啶、鸟嘌呤与啶，或简称A、C、G、T。

This attaches methyl groups (a carbon atom and three hydrogens) to either adenine or cytosine, two of the four chemical bases that form the alphabet of DNA, depending on the gene involved.

该作用可以让甲基（由一个碳原子和三个氢原子组成）附着于嘌呤或胞啶上——组成DNA序列四种主化学成分中两种，到底附着是哪种取决于涉及到基因种类。