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  • 生物技术和法医学 -- -- 高级

    DNA Fingerprinting

    What's a DNA fingerprint? 
    ::什么是DNA指纹?

    fingerprinting creates a pattern based on an individual's unique DNA. This can be used as a unique identifier for a person. As you can imagine, this would be a key tool for the forensic scientist.
    ::指纹指纹创造了基于个人独特DNA的模式。 这可以用作一个人的独特身份识别符。 正如您可以想象的那样, 这将是法医科学家的关键工具 。

    Applications of DNA Technology: Forensic DNA Analysis
    ::DNA应用技术:法医DNA分析

    You know that DNA can be used to distinguish individuals from each other. You may have heard that DNA can also be used to match evidence and suspects and help solve crimes. This is demonstrated on shows like CSI: Crime Scene Investigation . But how is this done? How is a genetic or DNA fingerprint , which is a DNA pattern unique to each individual (except identical twins), created? Genetic fingerprinting, or DNA fingerprinting, distinguishes between individuals of the same using only samples of their DNA. DNA fingerprinting has thus become one of the most powerful tools of forensic scientists, enabling law enforcement personnel to match biological evidence from crime scenes to suspects. As any two humans have the majority of their DNA sequence in common, those sequences that demonstrate high variability must be analyzed. This DNA analysis was first developed using DNA hybridization techniques, but now is almost exclusively PCR-based.
    ::您知道DNA可以用来区分个人。 您可能听说过DNA也可以用来匹配证据和嫌疑人, 并帮助解决犯罪。 这一点在CSI : 犯罪场景调查 。 但是如何做到呢? 基因或DNA指纹是如何形成的? 基因或DNA指纹是每个人特有的DNA模式( 双胞胎除外 ) ? 基因指纹或DNA指纹可以仅仅使用DNA样本来区分同一个人。 DNA指纹因此成为法医科学家中最有力的工具之一,使执法人员能够将犯罪现场的生物证据与嫌疑人相匹配。 任何两人的DNA序列都具有共性,因此必须分析显示高度变异性的序列。 DNA分析最初是使用DNA混合技术开发的,但现在几乎完全以PCR为基础。

    DNA fingerprinting was developed by Sir Alec Jeffreys in 1985. Genetic fingerprinting exploits highly variable repeating sequences. Two categories of these sequences are microsatellites and minisatellites. Microsatellites , also known as short tandem repeats (STRs) , consist of adjacent repeating units of 2 - 10 bases in length, for example (GATC) n , where GATC is a tetranucleotide (4 base) repeat and n refers to the number of repeats. It is the number of repeating units at a given locus that is variable. An STR profile can be created for any individual by analyzing a series of STRs ( Figure  ). Two unrelated humans will be unlikely to have the same numbers of repeats at a given locus.
    ::Alec Jeffrey爵士于1985年开发了DNA指纹。遗传指纹利用了高度变异的重复序列。这些序列有两类:微型卫星和微型卫星。微型卫星,又称短连线重复(STS),由相邻的2至10个基数重复单元组成,例如(GATC)n,GATC是四核分裂物(4个基数)重复,N指重复次数。在特定位置的重复单位数量是可变的。通过分析一系列TRS(Figure ),可以为任何个人创建STS剖面图。两个无关的人在特定位置不太可能有相同数量的重复。

    In STR profiling, is used to obtain enough DNA then to detect the number of repeats at 13 specific loci. PCR products are separated by gel or capillary electrophoresis. (Capillary electrophoresis is similar to gel electrophoresis but uses a capillary tube filled with the gelatin material.) By examining enough STR loci and counting how many repeats of a specific STR sequence there are at a given locus, it is possible to create a unique genetic profile of an individual. STR analysis has become the prevalent analysis method for determining genetic profiles in forensic cases. It is possible to establish a match that is extremely unlikely to have arisen by coincidence, except for identical twins, who will have identical genetic profiles. The polymorphisms (different in the number of repeats) displayed at each STR region will be shared by approximately 5 - 20% of individuals. When analyzing STRs at multiple loci, such as the 13 STRs analyzed in forensic DNA analysis, it is the unique combinations of these polymorphisms in an individual that make this method unmatched as an identification tool. The more STR regions that are analyzed in an individual the more discriminating the test becomes.
    ::在STR特征分析中,利用足够的DNA,然后在13个特定地点检测重复次数。PCR产品被凝胶或毛细电极分离。(Capillary 电极与凝胶电极相似,但使用充满凝胶材料的毛细管。 )通过检查足够的STLLoci并计算某个特定地点具体可疑交易序列的重复次数,可以建立个人独特的基因特征。在法医DNA分析中分析的13件可疑交易分析是确定法医案件遗传特征的常用分析方法。有可能确定一种极不可能由巧合产生的匹配,但具有相同基因特征的同双胞胎除外。在每个TRT区域显示的多种形态(重复次数不同)将约有5-20%的人共享。在多个地方分析可疑交易时,例如在法医DNA分析中分析的13件可疑交易时,这些多元形态的独特组合使得这种方法不匹配为一种识别工具。在个人中,更具有歧视性的区域将更能分析个人测试。

    Genetic fingerprinting is used in forensic science to match suspects to samples of , hair, saliva or semen , or other sources of DNA. It has also led to several exonerations of formerly convicted suspects. Genetic fingerprinting is also used for identifying human remains, testing for paternity, matching organ donors, studying of wild , and establishing the province or composition of foods. It has also been used to generate hypotheses on the pattern of human .
    ::在法医学中,遗传指纹用于将嫌疑人与样本、毛发、唾液或精液或其他DNA来源相匹配,还导致对以前被定罪的嫌疑人的若干免责,遗传指纹还用于识别遗骸、鉴定亲子关系、匹配器官捐献者、研究野生生物、确定省份或食物构成,还被用于产生关于人类形态的假设。

    CODIS
    ::CODIS coDIS coDIS coDIS

    In the United States, DNA fingerprint profiles generated from the 13 STR loci are stored in The National DNA Index (NDIS), part of CODIS , The Combined DNA Index System, maintained by the Federal Bureau of Investigation. As of June 2012, CODIS maintained over 9.7 million offender profiles, 1.1 million arrestee profiles and 436,000 forensic profiles. Profiles maintained in CODIS are compiled from both suspects and evidence, and therefore are used to help solve criminal cases. Also as of June 2012, CODIS has produced over 182,200 "hits," assisting in more than 174,600 investigations.
    ::在美国,由13份可疑交易报告生成的DNA指纹档案储存在由联邦调查局维护的DNA综合索引系统 " 国家DNA索引 " (DNA索引)中,截至2012年6月,DNA综合索引系统保存了970多万罪犯档案、110万被捕者档案和436,000份法医档案,从嫌疑人和证据中收集了13份可疑交易报告保存的DNA指纹档案,因此用于帮助解决刑事案件,截至2012年6月,DNA综合索引系统还制作了182,200多份 " 线索 " ,协助174,600多项调查。

    Profiles of missing persons are also maintained in CODIS. The true power of STR analysis is in its statistical power of discrimination. Because the 13 loci are independently assorted, the laws of probabilities can be applied. This means that if someone has the genotype of ABC at three independent loci, then the of having that specific genotype is the probability of having type A times the probability of having type B times the probability of having type C. This has resulted in the ability to generate match probabilities of 1 in a quintillion (1 with 18 zeros after it) or more, that is, the chance of two samples matching by coincidence is greater than the number of people on the planet, or the number of people that have ever lived.
    ::CODIS中也保留了失踪人员的概况。可疑交易报告分析的真正力量在于其统计上的歧视力量。由于13个地点是独立的,因此可以适用概率法则。这意味着如果某人在3个独立的地点具有ABC基因型,那么具体基因型的概率是A型的概率乘以B型的概率乘以C型的概率的概率。这导致能够产生五分之一的概率(1个和18个零)或更多的概率,也就是说,两个样本相匹配的机会大于地球上的人数或曾经生活过的人数。

    lesson content
    The CODIS loci were analyzed by STR analysis. Notice they are spread over 14 chromosomes and that two are on the X and Y chromosomes.

    The of PCR has enabled STR analysis to become the method of choice for DNA identification. Prior to PCR, other methods were utilized. These include restriction fragment length polymorphism (RFLP) analysis and Southern blot analysis.
    ::PCR使STR分析成为DNA鉴定的首选方法,在PCR之前,使用了其他方法,包括限制碎片长度多形态分析(RFLP)和南方草块分析。

    RFLP Analysis: Restriction Fragment Length Polymorphism
    ::RFLP 分析:限制碎片长度的多元性

    Prior to the development of PCR, restriction digestion of DNA followed by Southern blot analysis was used for DNA fingerprinting. This analysis is based on the polymorphic nature of restriction enzyme sites among different individuals, hence restriction fragment length polymorphisms (RFLP) are formed after digestion of DNA with these enzymes. A Southern blot , named after its inventor Edwin Southern, is a method used to check for the presence of a specific DNA sequence in a DNA sample. Once an individual’s DNA is digested with a specific restriction enzyme, the resulting fragments are analyzed by Southern blot analysis. These fragments will produce a specific pattern for that individual. Southern blotting is also used for other molecular biology procedures, including gene identification and isolation. Other blotting methods that employ similar principles have been developed. These include the western blot and northern blot. These procedures analyze and , respectively.
    ::在开发PCR之前,对DNA进行限制消化,然后进行南方染色体分析,然后对DNA进行限制消化,然后进行南方染色体指纹鉴定。这一分析基于不同个人之间限制酶点的多元形态性质,因此在用这些酶消化DNA后形成限制碎片长度的多元形态(RFLP)。以其发明家Edwin South命名的南方染色体是一种方法,用来检查DNA样本中是否存在具体的DNA序列。一旦一个人的DNA经过特定限制酶的消化,则由南方染色体分析其产生的碎片。这些碎片将为该个人产生一种特定模式。南方染色体还用于其他分子生物学程序,包括基因识别和隔离。还开发了采用类似原则的其他染色法。这些方法包括西方染色体和北部染色体。这些程序分别分析和分析。

    RFLP and Southern blot analysis involved several steps:
    ::RFLP和South Blot分析包括若干步骤:

    1. First, the DNA being analyzed is cut into different-sized pieces using restriction enzymes.
      ::首先,正在分析的DNA被用限制酶切割成不同尺寸的片段。
    2. The resulting DNA fragments are separated by gel electrophoresis.
      ::由此产生的DNA碎片用凝胶电光分离出来。
    3. Next, an alkaline solution or heat is applied to the gel so that the DNA denatures and separates into single strands.
      ::其次,对凝胶应用碱溶液或热,以便DNA的密度分解成单线。
    4. Nitrocellulose paper is pressed evenly against the gel and then baked so the DNA is permanently attached to it. The DNA is now ready to be analyzed using a radioactive single-stranded DNA probe in a hybridization reaction.
      ::硝基纤维素纸对凝胶均匀地压压,然后烘烤,这样DNA就永久附着在凝胶上。 DNA现已准备在混合反应中用放射性单层DNA探测器进行分析。
    5. After hybridization, excess probe is washed from the membrane, and the pattern of hybridization is visualized on X-ray film by autoradiography ( Figure  ).
      ::混合后,过量探测器从膜中冲出,通过自动放射法在X射线胶片上可视化模式(图)。
    lesson content
    Mutations can create or abolish restriction enzyme (RE) recognition sites, thus affecting quantities and length of DNA fragments resulting from RE digestion.

    Hybridization is when two genetic sequences bind together because of the hydrogen bonds that form between the base pairs. To make hybridization work, the radioactive probe has to be denatured so that it is single-stranded. The denatured probe and the Southern blot are incubated together, allowing the probe to bind to the corresponding fragment on the Southern blot. The probe will bond to the denatured DNA wherever it finds a fit. Hybridization of a probe made to a variable segment of DNA will produce a DNA fingerprint pattern specific for an individual. This procedure has a number of steps and is very labor intensive. PCR-based methods are much simpler.
    ::混合化是指两个基因序列因基对之间形成的氢系而结合在一起。 要使混合化工作, 放射性探测器必须变色, 以便进行单层试验。 硬质探测器和南色块是一起孵化的, 使探测器能够与南色块上的相应碎片结合。 该探测器在发现合适的地方会与刻度DNA结合。 将探测器与DNA的可变部分混合起来, 将产生一个人特有的DNA指纹模式。 这个程序有若干步骤, 劳动强度非常大 。 基于PCR 的方法简单得多 。

    Summary
    ::摘要

    • Genetic fingerprinting, or DNA fingerprinting, distinguishes between individuals of the same species using only samples of their DNA.
      ::基因指纹或DNA指纹只使用DNA样本,对同一物种的个人加以区分。
    • DNA fingerprinting has become one of the most powerful tools of the forensic scientist, enabling law enforcement personnel to match biological evidence from crime scenes to suspects.
      ::DNA指纹已成为法医科学家最有力的工具之一,使执法人员能够将犯罪现场的生物证据与嫌疑人的生物证据相匹配。

    Review
    ::回顾

    1. What is a DNA fingerprint and how is it used?
      ::DNA指纹是什么? 它是如何使用的?
    2. What is STR profiling?
      ::什么是可疑交易报告简况分析?
    3. What is CODIS? What is it used for?
      ::CODIS是什么 用来做什么
    4. What are the five steps in RFLP and Southern blot analysis?
      ::" 自由劳工 " 和 " 南方草块 " 分析的五个步骤是什么?
    5. What is hybridization in regards to RFLP?
      ::关于拉加人民解放阵线,什么是混合化?