DNA Fingerprinting - Definition, Principle, Steps, Applications & Diagram
DNA fingerprinting is a technique used to identify individuals based on unique genetic patterns. From crime scene analysis to genetic disorder detection, this method plays a pivotal role in modern science and biotechnology.
This Story also Contains
- What is DNA Fingerprinting?
- Principles of DNA Fingerprinting
- DNA Fingerprinting Steps
- Techniques of DNA Fingerprinting
- Applications of DNA Fingerprinting
- DNA Fingerprinting Practice Questions for NEET
- FAQs on DNA Fingerprinting
- Recommended Video for DNA Fingerprinting
What is DNA Fingerprinting?
DNA Fingerprinting, also known as DNA Profiling, is a procedure that reveals the genetic makeup of any living organism. Differentiation of one person from another is made through variations in their satellite DNA regions. This has brought a revolutionary change in the field of modern science, particularly in forensic and genetic studies.
DNA fingerprinting was first discovered in the 1980s. In 1984, the British geneticist Dr Alec Jeffreys discovered a breakthrough technique, eventually creating a powerful tool for genetic identification and analysis.
DNA fingerprinting is vital in many applications and areas, including forensic science and paternity testing. It is highly applied in the disclosure of crime scenes, diagnosis of genetic diseases, and understanding of biological evolution.
Commonly Asked Questions
DNA fingerprinting is a technique used to identify and compare individuals based on their unique DNA patterns. It analyzes specific regions of DNA that vary between individuals, creating a "genetic fingerprint" that is highly specific to each person.
The terms are often used interchangeably, but DNA profiling typically refers to the broader process of analyzing genetic markers for identification purposes. DNA fingerprinting specifically refers to the technique of creating a visual representation of an individual's DNA pattern.
Traditional DNA fingerprinting cannot distinguish between identical twins as they share the same DNA. However, advanced techniques that look at epigenetic modifications or rare mutations that occur after fertilization can potentially differentiate between identical twins.
Limitations include the need for a sufficient quantity and quality of DNA, the possibility of contamination, the potential for human error in analysis, and the fact that it can't determine when DNA was deposited at a crime scene. It also can't distinguish between identical twins using standard methods.
While DNA fingerprinting itself isn't used in personalized medicine, the underlying principles and technologies contribute to genetic testing that can identify disease risks, predict drug responses, and tailor treatments to an individual's genetic profile.
Principles of DNA Fingerprinting
The principle of DNA fingerprinting is that every person has a unique DNA pattern, except identical twins. It studies specific regions in DNA, like VNTRs and STRs, which show differences between individuals. These differences help in identifying people for use in forensics, paternity tests, and biotechnology.
Genetic Uniqueness
DNA fingerprinting is based on the fact that every person, except for identical twins, will have a unique DNA sequence.
Polymorphic Regions in DNA
DNA has very polymorphic regions, for instance, Short Tandem Repeats (STRs) and Variable Number Tandem Repeats (VNTRs), that exhibit great differences among individuals and are, therefore, hyper-informative for genetic identification.
Structure of STRs and VNTRs
Commonly Asked Questions
The principle behind DNA fingerprinting is that certain regions of DNA (called Variable Number Tandem Repeats or VNTRs) vary in length between individuals. By analyzing these regions, scientists can create a unique genetic profile for each person.
Unlike traditional fingerprinting that relies on physical patterns on fingertips, DNA fingerprinting examines genetic material. It's more accurate, can be performed with minimal biological samples, and can identify individuals even when traditional fingerprints are unavailable.
Nuclear DNA fingerprinting analyzes DNA from the cell nucleus, which is inherited from both parents. Mitochondrial DNA fingerprinting examines DNA from mitochondria, which is inherited only from the mother. Mitochondrial DNA is often used when nuclear DNA is degraded or unavailable.
While traditional DNA fingerprinting doesn't predict physical traits, advanced genetic analysis techniques can provide some information about physical characteristics like eye color, hair color, and ancestry. This field, known as forensic phenotyping, is still developing and has limitations.
In paternity testing, DNA fingerprints of the child, mother, and alleged father are compared. Since a child inherits half of their DNA from each parent, the child's DNA fingerprint should show a 50% match with each biological parent, allowing for determination of paternity.
DNA Fingerprinting Steps
DNA fingerprinting involves a series of steps to identify genetic patterns. These include collecting samples, isolating DNA, cutting it using enzymes, and analyzing it through gel electrophoresis. Each step helps create a unique DNA profile for an individual.
Sample Collection
DNA could be extracted from blood, hair, saliva, and skin cells, amongst others. Care should always be taken to ensure the cleanliness and purity of the sample for the best results.
Isolation of DNA
DNA extraction from preserved samples did not distort or contaminate the sample in any way.
DNA Extraction Process
Digestion of DNA by Restriction Endonucleases
Restriction enzymes work on cutting DNA at precise recognition sites, thereby creating a specific pattern of DNA fragments. The DNA fingerprint is then composed of these fragments.
The action of Restriction Endonucleases on DNA
Gel Electrophoresis
DNA fragments are sorted by size using agarose gel electrophoresis and an electric field. This step images the DNA bands.
Blotting
The DNA fragments are transferred from the gel onto a nylon or nitrocellulose membrane in preparation for hybridisation.
Hybridisation Using Labelled Probe
The transferred membrane strands of DNA are exposed to labelled DNA probes, which are complementary to the known DNA sequences to be measured. The unique DNA patterns are thus highlighted.
Autoradiography
Autoradiography exposes the radiolabeled DNA probes to the separated fragments of DNA on the membrane, revealing unique DNA band patterns for different individuals.
Commonly Asked Questions
The main steps in DNA fingerprinting are: 1) DNA extraction from a biological sample, 2) DNA amplification using PCR, 3) Cutting DNA into fragments using restriction enzymes, 4) Separating DNA fragments by size using gel electrophoresis, 5) Transferring DNA to a membrane (Southern blotting), 6) Probing for specific DNA sequences, and 7) Visualizing and analyzing the results.
The time required for DNA fingerprinting can vary depending on the method used and the complexity of the sample. With modern techniques, results can be obtained in as little as 24-48 hours, but more complex cases may take several days to weeks.
DNA fingerprinting has evolved from using RFLP analysis, which required large amounts of DNA, to PCR-based methods that can work with minute samples. Modern techniques use automated sequencing and can analyze multiple DNA markers simultaneously, increasing speed and accuracy.
Yes, DNA fingerprinting can often be performed on degraded or old samples, thanks to PCR technology which can amplify even small amounts of DNA. However, the quality of results may be affected, and special techniques might be needed for highly degraded samples.
DNA databases store genetic profiles from various sources, including convicted criminals, crime scene evidence, and sometimes voluntary contributors. They allow for rapid comparison of DNA profiles, helping to solve crimes and identify individuals.
Techniques of DNA Fingerprinting
Different techniques are used to perform DNA fingerprinting based on the type of sample and purpose. Common methods include RFLP, PCR, STR analysis, and mitochondrial DNA testing. Each technique has its own advantages in terms of speed, accuracy, and sensitivity. The methods of DNA fingerprinting are described below:
RFLP (Restriction Fragment Length Polymorphism)
RFLP studies the variability in the lengths of DNA fragments digested by restriction enzymes. This technique, although not in use so frequently at present, was one of the earliest methods of DNA profiling.
PCR (Polymerase Chain Reaction)
PCR helps to amplify desired DNA fragments, making it possible to look for analysis in very small amounts of DNA. PCR is a popular technique, as it is fast and very sensitive.
STR Analysis
Short Tandem Repeats (STR) analysis is the most commonly used technique at present for DNA fingerprinting. It studies only specific areas of DNA that show hypervariability between individuals.
Mitochondrial DNA Analysis
Mitochondrial DNA analysis is used for studying ancient DNA and tracing the maternal lineage. It can often be the only source of DNA in forensic applications due to the lack of DNA in the nucleus.
Applications of DNA Fingerprinting
DNA fingerprinting is used in many fields like forensic science, medicine, and research. It helps identify criminals, prove biological relationships, and diagnose genetic diseases. It is also useful in studying human evolution and biodiversity.
Forensic Science
It is an essential technique in forensic science for use in crime scene investigations and paternity testing.
Medical Applications
It is involved in the clinical diagnosis of genetic disorders and matching tissues for transplants to develop a personalized medicine system.
Biological Research
In evolutionary biology and population genetics, DNA fingerprinting studies genetic variability and the evolutionary relationship among species.
DNA Fingerprinting Practice Questions for NEET
Q1. On average, how many percent of the DNA between two humans is the same?
99%
99.9%
95%
100%
Correct answer: 2) 99.9%
Correct answer:
In terms of DNA composition, all humans are 99.9% genetically similar, with the differences confined to the remaining 0.1%. This small variation plays a crucial role in determining individual traits and susceptibility to diseases. The genetic differences in this 0.1% provide valuable insights into the causes of various diseases, as they often include mutations, polymorphisms, or variations that influence health, response to treatments, and disease risk.
Hence the correct answer is option 2) 99.9%
Q2. Who developed the DNA Fingerprinting technique?
Alec Jeffreys
Francis Crick
James Watson
None of above
Correct answer: 1) Alec Jeffreys
Explanation:
Sir Alec Jeffreys was the first to construct DNA fingerprinting in the 1980s, based at the University of Leicester as both a professor and a geneticist. He used satellite DNAs, more scientifically referred to as variable number tandem repeats (VNTRs), in detecting differences in the genetics of different humans. This innovative method allowed the efficient detection of individuals and turned criminal investigations and paternity testing upside down by comparing the samples with unique genetic profiles.
Hence the correct answer is Option 1) Alec Jeffreys.
Q3. Choose the correct flow of DNA fingerprinting steps:
Isolating the DNA→Digesting the DNA→Separating the digested fragments→Blotting the separated fragments→Hybridising the fragments→ Analysing the hybrid fragments
Isolating the DNA→Separating the digested fragments→Digesting the DNA→Blotting the separated fragments→Hybridising the fragments→ Analysing the hybrid fragments
Isolating the DNA→Separating the digested fragments→Digesting the DNA→Hybridising the fragments→Blotting the separated fragments→ Analysing the hybrid fragments
Isolating the DNA→Digesting the DNA→Separating the digested fragments→Hybridising the fragments→ Blotting the separated fragments→Analysing the hybrid fragments
Correct answer: 1) Isolating the DNA→Digesting the DNA→Separating the digested fragments→Blotting the separated fragments→Hybridising the fragments→ Analysing the hybrid fragments
Explanation:
DNA isolation: Extracting DNA from a sample (such as blood, hair, etc.) is the initial step.
DNA digestion: Using specialized enzymes known as restriction enzymes, which can identify and cut DNA at particular sequences, the extracted DNA is subsequently broken up into smaller pieces.
Sorting the digested fragments: A method known as gel electrophoresis is used to separate the DNA fragments based on size. Larger fragments pass through the gel more slowly than smaller ones.
Blotting the separated fragments: Southern blotting is the act of transferring the separated DNA fragments onto a membrane, often a nitrocellulose or nylon membrane.
Hybridizing the fragments: To identify the DNA fragments of interest, the membrane containing the fragments is subsequently exposed to a tagged probe, which is a brief DNA sequence complementary to a particular sequence in the DNA fragments.
Analyzing the hybrid fragments: The DNA fingerprint is created by analyzing the patterns of the hybridized fragments after the tagged probe has been found. Each person has a pattern.
Hence, the correct answer is option 1)Isolating the DNA → Digesting the DNA → Separating the digested fragments → Blotting the separated fragments → Hybridising the fragments → Analysing the hybrid fragments.
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FAQs on DNA Fingerprinting
Q1. What is DNA fingerprinting?
It is a genetic technique that identifies individuals based on unique DNA patterns, especially VNTRs and STRs.
Q2. What is the principle behind DNA fingerprinting?
The principle is based on polymorphism in DNA sequences, where individuals have unique patterns in repetitive DNA regions.
Q3. What are the main steps involved in DNA fingerprinting?
The main steps are sample collection, isolation of DNA, digestion of DNA by restriction enzyme, separation by gel electrophoresis, hybridization with DNA probes, and autoradiography.
Q4. What are the major applications of DNA fingerprinting?
Major applications include criminal identification, paternity testing, identifying remains, and studying genetic diversity.
Recommended Video for DNA Fingerprinting
Frequently Asked Questions (FAQs)
STR (Short Tandem Repeat) fingerprinting looks at the number of repeats in specific DNA regions, while SNP (Single Nucleotide Polymorphism) fingerprinting examines single base pair variations. SNP analysis can provide more detailed genetic information but requires more advanced technology.
The future of DNA fingerprinting likely involves faster, more portable technologies for rapid on-site analysis, increased integration with other biometric data, more comprehensive genetic analysis beyond just identification, and the ability to extract more information from smaller or more degraded samples. Ethical considerations and privacy protections will continue to be important as the technology advances.
While traditional DNA fingerprinting doesn't directly study epigenetics, related techniques can analyze epigenetic modifications like DNA methylation. This helps in understanding how environmental factors affect gene expression without changing the DNA sequence.
DNA fingerprinting techniques are used to identify genetic markers associated with behavioral traits. While behavior is complex and influenced by many factors, these studies help understand the genetic components of personality, mental health conditions, and cognitive abilities.
While not directly used in nutrigenomics, DNA fingerprinting technologies contribute to identifying genetic variations that influence nutrient metabolism and dietary responses. This helps in developing personalized nutrition strategies based on an individual's genetic profile.
Mitochondrial DNA is useful in forensics because it's abundant in cells and can often be recovered from degraded samples. It's inherited maternally, making it valuable for tracing maternal lineages and identifying remains when nuclear DNA is unavailable.
In paleogenetics, DNA fingerprinting techniques are adapted to analyze highly degraded DNA from ancient specimens. This allows scientists to study the genetics of extinct species, trace human evolution, and understand historical population dynamics.
DNA fingerprinting techniques are used to identify and characterize the diverse microorganisms in the human microbiome. This helps in understanding the composition of microbial communities, their impact on health, and how they vary between individuals or populations.
While not directly used in pharmacogenomics, DNA fingerprinting technologies contribute to identifying genetic variations that influence drug responses. This helps in developing personalized medication strategies based on an individual's genetic profile.
Population databases contain DNA profiles from various populations. They're crucial for calculating the statistical significance of a DNA match, understanding the distribution of genetic markers in different groups, and ensuring the accuracy of DNA evidence in diverse populations.