是構成遺傳的基本單位；編碼蛋白所有信息的DNA序列。從結構上來講，基因包含三個區域：稱為啟動子的調節區域；與其并列的編碼蛋白質的密碼子區域；以及3'端尾部序列。在哺乳動物細胞里，啟動子是一個包含著許多蛋白質結合位點的復雜區域，它調節基因的表達。單個基因可以被激活，由這些控制蛋白決定時間、地點及蛋白表達量，從而產生蛋白質。這一過程稱為基因表達。在人類基因組中，大約有10萬個基因。其中一些進化過程相關聯而形成 "基因家族"表達相關蛋白。也有基因不再制造蛋白，這些進化中的殘余物稱為假基因。

The basic unit of heredity; the sequence of DNA that encodes all the information to make a protein. Structurally, a gene is formed by three regions: a regulatory region called the promoter juxtaposed to the coding region containing the protein sequence, and a “3’ tail” sequence. In mammalian cells, the promoter is a complex region containing binding sites for many proteins that regulate gene expression. A gene may be “activated” or “switched on” to make protein – this activation is referred to as gene expression - by these proteins which control when, where and how much protein is expressed from the gene. In the human genome, there are an estimated 100,000 genes. Some of these are evolutionarily related and form“gene families” that express related proteins. There are also genes that no longer make a protein; these defective remnants of evolution are called pseudogenes.