Replicação do DNA
International Baccalaureate · IB Diploma · Biology · SL Tópico 24 4:39 Narração em inglês · Legendas em inglês + 中文 gravadas
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After DNA replication, each daughter double helix contains one pre-existing strand and one newly synthesized strand.
DNA复制后，每个子代双螺旋都含有一条原有链和一条新合成链。
Copying a molecule is different from expressing its information.
复制分子与表达其信息是不同的过程。
DNA replication is semi-conservative.
DNA复制是半保留的。
Complementary base pairing supports copying of the base sequence: adenine pairs with thymine and cytosine with guanine.
互补碱基配对支持碱基序列的复制：腺嘌呤与胸腺嘧啶配对，胞嘧啶与鸟嘌呤配对。
The strands have opposite orientations.
两条链具有相反的取向。
Helicase separates paired strands, while DNA polymerase builds new DNA using a template and available nucleotides.
解旋酶分离配对的链，而DNA聚合酶利用模板和可用的核苷酸合成新的DNA。
Semi-conservative replication is DNA copying in which each daughter double helix retains one parental strand.
半保留复制是指DNA复制过程中，每个子代双螺旋都保留一条亲本链。
DNA polymerase is an enzyme that synthesizes DNA using a template.
DNA聚合酶是一种利用模板合成DNA的酶。
Complementary bases support copying of the template sequence.
互补碱基支持模板序列的复制。
Distinguish DNA copying from transcription into RNA and from separation of chromosomes in cell division.
请将DNA复制与转录为RNA以及细胞分裂中染色体的分离区分开来。
The labelled-strand prediction assumes complete replication rounds and no exchange or degradation of the original material.
标记链预测假设复制轮次完整，且原始材料没有发生交换或降解。
Detailed fork direction and fragment mechanisms remain in the separate HL preparation case pending guide review.
详细的叉方向和片段机制保留在单独的HL准备案例中，等待指南审查。
In the lab: Use labelled strand models or an attributed experimental diagram.
在实验室中，使用带标记的链模型或标注的实验示意图。
Mark old and new material with both labels and colours so the meaning survives monochrome viewing.
用标签和颜色同时标记旧材料和新材料，以确保单色观看时仍能理解其含义。
Track successive rounds using a stated starting population and assumptions.
利用明确的初始种群和假设来追踪连续复制轮次。
A classroom model illustrates predictions; it is not direct evidence about enzyme activity or a substitute for experimental results.
课堂模型用于说明预测结果；它并非关于酶活性的直接证据，也不能替代实验结果。
Known: one double-stranded molecule contains two labelled original strands.
已知：一个双链分子包含两条标记的原始链。
After one complete round in unlabelled nucleotides, two molecules each contain one labelled strand.
在未标记核苷酸中经过一轮完整复制后，两个分子各含一条标记链。
After two rounds, four molecules exist: two retain one labelled original strand and two contain only unlabelled strands.
经过两轮复制后，共有四个分子：其中两个保留一条标记的原始链，另外两个仅含未标记链。
The fraction containing an original strand is two over four, which equals fifty percent.
含有原始链的分子比例为四分之二，即百分之五十。
Your turn: One labelled double helix replicates for three complete rounds in unlabelled nucleotides.
轮到你了。 一条标记的双螺旋在未标记的核苷酸中复制三轮完整周期。
What percentage of the eight molecules contain an original strand?
这八个分子中含有原始链的百分比是多少？
Pause the video and work it out.
请暂停视频，自己算一算。
Check: the two original strands end up in 2 of the 8 molecules, which is 25 percent.
核对：两条原始链分在 8 个分子中的 2 个里，即 25%。
Replication uses DNA as a template to make DNA.
复制以DNA为模板合成DNA。
Transcription uses a DNA template to make RNA.
转录以DNA为模板合成RNA。
A predicted label distribution assumes complete rounds and no degradation or exchange of the labeled material.
预测的标记分布假设经历了完整的复制轮次，且标记物质未发生降解或交换。
Not true: DNA replication and transcription both produce the same type of nucleic-acid product.
不正确。 DNA复制和转录产生的核酸产物类型相同。
Replication copies DNA into DNA; transcription copies a DNA template into RNA.
复制将DNA拷贝为DNA，而转录以DNA为模板合成RNA。
The products are different nucleic acids with different roles.
两者的产物是不同的核酸，功能也不同。
DNA replication is semi-conservative.
DNA复制是半保留的。
Complementary bases support copying of the template sequence.
互补碱基支持模板序列的拷贝。
Watch for: replication uses DNA as a template to make DNA; transcription uses a DNA template to make RNA.
请注意：复制以DNA为模板合成DNA；转录以DNA为模板合成RNA。
One labelled double helix replicates for four rounds in unlabelled nucleotides.
一个标记的双螺旋在未标记的核苷酸中复制了四轮。
Find the percentage of the 16 molecules that still contain a labelled strand.
找出仍含有标记链的16个分子所占的百分比。
Replication makes DNA.
复制产生DNA。
Transcription makes RNA.
转录产生RNA。
Each parent strand acts as a template.
每条亲代链都作为模板。
A new strand is built along each one, so every daughter molecule keeps one old strand and gains one new strand.
沿每条模板合成一条新链，所以每个子代分子保留一条旧链，并获得一条新链。
One fully labelled double helix undergoes 4 complete rounds in unlabelled nucleotides.
一个完全标记的双螺旋在不含标记的核苷酸中经历四轮完整的复制。
Find the fraction of molecules with any original strand and explain why original strands do not multiply.
求含有任意原始链的分子所占的比例，并解释为什么原始链不会倍增。
Two original strands persist among 16 molecules, so 2 of the 16 molecules, one eighth or 12.5 percent, carry an original strand.
两条原始链保留在 16 个分子中，所以 16 个分子里有 2 个、即八分之一或 12.5% 含有原始链。
Templates are retained while new strands are synthesized; assume no degradation or strand exchange.
新链合成时模板链被保留；这里假设没有降解或链交换。
This does not require unsupported fork detail.
这并不需要额外的复制叉细节。
Pause and check yourself. Explain each point on screen in your own words, then change one number in the last example and say which assumption must still hold.
暂停一下，自我检查：用自己的话解释屏幕上的每个要点，再改动最后一个例子中的一个数字，说明哪个假设仍然必须成立。