Replication of DNA and RNA · DNA 与 RNA 的复制
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| replication/ˌreplɪˈkeɪʃn/ | 复制 | fù zhì |
| semi-conservative/ˈsemi kənˈsɜːvətɪv/ | 半保留 | bàn bǎo liú |
| template/ˈtempleɪt/ | 模板 | mú bǎn |
| DNA polymerase/ˌdiː en ˈeɪ ˌpɒlɪməˈreɪz/ | DNA聚合酶 | DNA jù hé méi |
| lagging strand/ˈlæɡɪŋ strænd/ | 后随链 | hòu suí liàn |
| leading strand/ˈliːdɪŋ strænd/ | 前导链 | qián dǎo liàn |
| DNA ligase/ˌdiː en ˈeɪ ˈlɪɡeɪs/ | DNA连接酶 | DNA lián jiē méi |
| messenger RNA/ˈmesɪndʒə ˌɑː en ˈeɪ/ | 信使RNA | xìn shǐ RNA |
Copying DNA
- Before a cell divides, all its DNA must be copied — replication 复制.
- Each new molecule keeps one old strand and gains one new one.
- We call this semi-conservative 半保留 replication.
复制 DNA
- 在一个细胞分裂之前,它所有的 DNA 都必须被复制——复制(replication)。
- 每个新分子保留 一条旧链 并获得 一条新 链。
- 我们把这叫做 半保留(semi-conservative) 复制。
DNA replication is "semi-conservative" because each new molecule has: · DNA 复制是“半保留的”,因为每个新分子有:
Each daughter molecule conserves one parental strand and pairs it with one new strand. · 每个子分子保留一条亲本链,并把它与一条新链配对。
In semi-conservative replication, each new DNA molecule keeps one of the original strands. · 在半保留复制中,每个新 DNA 分子保留原始链之一。
That is exactly what "semi-conservative" means — one old strand is conserved in each copy. · 这正是“半保留”的意思——每个副本中保留一条旧链。
The steps of replication
- the double helix unwinds and the hydrogen bonds break, so the two strands separate.
- each old strand acts as a template 模板; free nucleotides pair with the exposed bases (complementary base pairing).
- the enzyme DNA polymerase DNA聚合酶 joins the new nucleotides into a strand — it can only add them in the 5′→3′ direction.
Semi-conservative DNA replication at a fork
复制的步骤
- 双螺旋 解开,氢键断开,所以两条链分开。
- 每条旧链充当一个 模板(template);自由的核苷酸与暴露的碱基配对(互补碱基配对)。
- 酶 DNA 聚合酶(DNA polymerase) 把新核苷酸连接成一条链——它只能以 5′→3′ 方向添加它们。
在一个复制叉处的半保留 DNA 复制
Semi-conservative replication · 半保留复制
Step through copying DNA. The helix unwinds, each old strand templates a new one, and you end with two identical molecules. · 一步步走过复制 DNA。螺旋解开,每条旧链作为模板复制一条新链,你最后得到两个相同的分子。
Free nucleotides line up against the exposed template bases by ______ base pairing. · 自由的核苷酸通过 ______ 碱基配对与暴露的模板碱基对齐。
Each template base attracts its complement (A–T, C–G), so the new strand is an exact partner. · 每个模板碱基吸引它的互补碱基(A–T、C–G),所以新链是一个精确的伙伴。
DNA polymerase adds new nucleotides: · DNA 聚合酶添加新核苷酸:
DNA polymerase can extend a strand only in the 5′→3′ direction, which is why the two strands are built differently. · DNA 聚合酶只能以 5′→3′ 方向延伸一条链,这就是为什么两条链以不同方式构建。
Leading and lagging strands 后随链
- Because of the 5′→3′ rule, the two new strands are built differently:
- the leading strand 前导链 is made continuously, following the unwinding.
- the lagging strand is made in short pieces, joined together by DNA ligase DNA连接酶.
DNA extracted from cells appears as pale, stringy strands.
前导链和后随链
- 由于 5′→3′ 规则,两条新链以不同方式构建:
- 前导链(leading strand) 连续地 制造,跟随解开。
- 后随链(lagging strand) 以 短片段 制造,由 DNA 连接酶(DNA ligase) 连接在一起。
从细胞中提取的 DNA 表现为苍白、丝状的链。
Put the steps of DNA replication in order. · 把 DNA 复制的步骤按顺序排列。
Unwind → expose templates → base-pair → join → two copies, each semi-conservative. · 解开 → 暴露模板 → 碱基配对 → 连接 → 两个副本,每个半保留。
RNA
- RNA is also made of nucleotides, but it is:
- a single strand,
- built with the sugar ribose, and
- uses uracil in place of thymine.
- Messenger RNA 信使RNA (mRNA) carries a copy of a gene's instructions out of the nucleus.
DNA: antiparallel strands held by complementary base pairs
RNA
- RNA 也由核苷酸构成,但它是:
- 单 链,
- 用糖 核糖(ribose) 构建,以及
- 用 尿嘧啶(uracil) 代替胸腺嘧啶。
- 信使 RNA(mRNA) 把一个基因指令的副本带出细胞核。
DNA:由互补碱基对保持的反平行链
How does RNA differ from DNA? · RNA 与 DNA 有什么不同?
RNA is a single strand with ribose sugar and uracil in place of thymine. · RNA 是一条带核糖、用尿嘧啶代替胸腺嘧啶的单链。
Match each feature to DNA or RNA. · 把每个特征与 DNA 或 RNA 配对。
DNA: double-stranded, deoxyribose, thymine. RNA: single-stranded, ribose, uracil. · DNA:双链、脱氧核糖、胸腺嘧啶。RNA:单链、核糖、尿嘧啶。
You've got it
- replication is semi-conservative: each new molecule keeps one old strand
- unwind → strands separate → each is a template → DNA polymerase joins nucleotides 5′→3′
- leading strand continuous; lagging strand in pieces joined by DNA ligase
- RNA: single strand, ribose, uracil (not thymine); mRNA carries the gene copy out of the nucleus
你掌握了
- 复制是 半保留的:每个新分子保留 一条旧链
- 解开 → 链分开 → 每条是一个 模板 → DNA 聚合酶 以 5′→3′ 连接核苷酸
- 前导 链连续;后随 链以片段由 DNA 连接酶 连接
- RNA:单链、核糖、尿嘧啶(不是胸腺嘧啶);mRNA 把基因副本带出细胞核