Molecular Biology
分子生物學
How does DNA make you who you are? In this lesson you will learn how DNA is built, how it copies itself through replication, how it makes proteins, and what happens when it changes.
DNA 怎樣造就了你？在這一課，你會學習 DNA 如何構成、如何透過複製來複製自己、如何製造蛋白質，以及當它改變時會發生甚麼。
1 · How DNA is built
DNA 的構成
DNA is made of units called nucleotides. Each nucleotide has a sugar, a phosphate and a base. There are four bases: A, T, C and G. A always pairs with T, and C always pairs with G. These are called base pairs.
DNA 由稱為核苷酸的單位組成。每個核苷酸有糖、磷酸和鹼基。有四種鹼基：A、T、C 和 G。A 總是與 T 配對，C 總是與 G 配對。這些稱為鹼基對。
2 · DNA replication
DNA 複製
Before a cell divides, it makes a copy of its DNA. The double helix unwinds, and each strand is used as a template to build a new matching strand. This is called DNA replication.
在細胞分裂前，它會複製自己的 DNA。雙螺旋解開，每條鏈用作模板來建立新的配對鏈。這稱為 DNA 複製。
3 · Making proteins
製造蛋白質
Genes contain the instructions to make proteins. First, transcription copies the DNA into messenger RNA. Then, translation reads the messenger RNA to build a protein from amino acids.
基因含有製造蛋白質的指令。首先，轉錄把 DNA 複製成信使 RNA。然後，轉譯讀取信使 RNA，用氨基酸建立蛋白質。
4 · Mutations
突變
A mutation is a change in the DNA sequence. Some mutations are harmless, some are harmful, and a few can be helpful. Mutations are the source of genetic variation.
突變是 DNA 序列的改變。有些突變無害，有些有害，少數可能有益。突變是基因變異的來源。
5 · Quick check
小測驗