The Science Behind DNA FINGERPRINTING || 3D ANIMATION || Class 11 || · Learn With 3D ANIMATION
通过犯罪现场调查，了解DNA指纹技术的原理与应用。适合练习生物、科技、犯罪调查相关词汇和表达。
Our objective is to learn about the technique and applications of DNA fingerprinting.
我们的目标是了解DNA指纹技术的原理及其应用。
Every single human being carries their own identity in their DNA.
每个人的DNA中都蕴含着他们独特的身份特征。
This unique identity is attributed to the 0 .1 % difference in the specific DNA pattern.
这种独特的身份特征，源于特定DNA序列中仅0.1%的差异。
Dr. Alec Jeffries in 1985 introduced a technique that gave genetic identity to an individual,
1985年，亚历克·杰弗里斯博士（Dr. Alec Jeffries）提出了一种技术，能够为个体确定其遗传身份。
known as DNA fingerprinting or DNA profiling.
这种方法被称为“DNA指纹识别”或“DNA谱型分析”。
Let us learn about the principle and technique of DNA through the investigation of a crime scene.
让我们通过调查犯罪现场来了解DNA的原理和技术。
But, what are they looking for?
但是，他们到底在寻找什么呢？
There is evidence left behind by the perpetrator like hair follicle, saliva,
犯罪者留下了诸如毛囊、唾液等证据。
semen, skilflakes or blood, where cells with nuclei can be isolated.
这些样本可以是精液、雪片或血液，其中含有可以分离出的带细胞核的细胞。
Blood samples can serve as evidence and are collected in a test tube.
血液样本可以作为证据，通常被收集在试管中。
Each drop of blood has small DNA pieces,
每一滴血液中都含有微小的DNA片段。
and this blood dissolves in a test tube with blood sample A.
这种血液会与血液样本A一起在试管中溶解。
The biological sample is sent to the forensic lab.
生物样本被送往法医实验室。
Let us call it sample A.
我们就把它称为样本A吧。
Here they have two more DNA samples, B and C, which have been collected from the suspects.
他们又获得了两份DNA样本（编号为B和C），这些样本是从嫌疑人身上采集的。
These samples are then treated to isolate their DNA, which is the first step of the DNA fingerprinting technique.
随后，这些样本会经过处理以分离出其中的DNA，这是DNA指纹鉴定技术的第一步。
A closer look at the DNA of each sample shows that it possesses coding and non -coding sequences.
仔细观察每个样本的DNA后发现，其中既包含编码序列，也包含非编码序列。
Here, the non -coding DNA has short nucleotide sequences which are organized as standard repeat.
在这里，非编码DNA包含一些短核苷酸序列，这些序列以标准重复单元的形式进行排列。
For example, the three highlighted parts are repeats of A, G, T, C, G, G, T in sample A.
例如，在样本A中，被高亮显示的这三个部分分别重复了序列“A、G、T、C、G、G、T”。
They
他们
are called VNTRs, also known as mini satellites.
这些被称为 VNTR（Very Small Near-Earth Orbit Radio Transmitters），也被称为“微型卫星”。
Similarly, we can see two highlighted regions of repeats in sample B and three highlighted regions of repeats in sample B.
同样地，我们可以在样本B中看到两个被标记为重复序列的区域，而在另一个样本B中则可以看到三个被标记为重复序列的区域。
Now the gel is subjected to an electric current to perform gel electrophoresis.
接下来，这种凝胶会被通以电流，从而进行凝胶电泳实验。
As the DNA is negatively charged it will start moving towards the positive pole or anode.
由于 DNA 带有负电荷，它会向正极（即阳极）移动。
Let us closely observe the movement of DNA fragments inside the gel.
让我们仔细观察凝胶内部DNA片段的移动情况。
The smaller fragments are quicker than the larger ones.
较小的碎片移动速度比较大的碎片快。
So they travel farther than the larger ones in the gel.
因此，它们在凝胶中的移动距离比那些较大的颗粒更远。
Thus, the DNA strands are separated depending on their length or number of base pairs.
因此，DNA链会根据其长度或碱基对的数量被分离开来。
This is the principle on which gel electrophoresis works for the separation of differently sized DNA.
这就是凝胶电泳分离不同大小DNA分子所依据的原理。
Now soak the gel in an alkali.
现在将这种凝胶浸泡在碱性溶液中。
This leads to the denaturation of the double -stranded DNA to its single -stranded form.
这一过程会导致双链DNA变性，从而转变为单链形式。
DNA is then blotted onto anylon or synthetic nitrocellulose membrane.
随后，将DNA转移到安纶（anylon）或合成硝化纤维素（synthetic nitrocellulose）膜上。
This technique is known as sudden blotting.
这种技术被称为“突然吸干法”（sudden blotting）。
It reproduces the distribution of the DNA fragments on the gel.
该图展示了DNA片段在凝胶上的分布情况。
The membrane is then immersed in a solution containing radioactive labeled probes.
随后，将该膜浸入含有放射性标记探针的溶液中。
Let us zoom into the membrane to closely observe the interaction of the sample DNA and the probe.
让我们将视角放大到细胞膜层面，仔细观察样本中的DNA与探针之间的相互作用。
These probes are the short nucleotide sequences complementary to the vntr.
这些探针是与 vntr 相互补的短核苷酸序列。
The probe hybridizes with the isolated DNA fragments.
该探针会与那些被分离出来的DNA片段发生杂交反应。
The extra probe is then washed off leaving behind only the radioactively labeled hybridized segments on the membrane.
随后，多余的探针会被冲洗掉，膜上仅留下那些经过放射性标记的、已经发生杂交的片段。
Now let us perform autoradiography.
现在我们来进行自动放射成像（autoradiography）实验吧。