DNA Fingerprinting Notes

 

DNA Fingerprinting

Introduction

Ø  DNA fingerprinting is a groundbreaking method used to identify individuals by analyzing unique patterns in their DNA.

Ø  DNA fingerprinting, also known as DNA profiling, is a method used to identify individuals based on their unique DNA characteristics. This technique has become an essential tool in forensic science, allowing for the identification of individuals involved in crimes.

Ø  The process focuses on variable number tandem repeats (VNTRs) or other polymorphic regions in the genome, particularly in the non-coding parts of DNA.

Ø  Although these regions do not code for proteins, they exhibit a high degree of variation from one person to another.

 

Steps of DNA Fingerprinting (DNA Fingerprinting Steps)

1. DNA Isolation

• Scientists collect a sample (e.g., from blood, hair follicles, saliva).

• The cells are broken open, and DNA is carefully extracted and purified.

2. Digestion with Restriction Enzymes

• Special proteins known as restriction endonucleases are used to cut the DNA at specific sequences.

• This creates fragments of varying lengths based on each individual’s unique repeat patterns.

3. Separation by Electrophoresis

• The DNA fragments are placed in a gel and subjected to an electric field.

• Smaller fragments move faster through the gel, thus separating DNA fragments according to size.

4. Blotting onto a Membrane

• The separated fragments from the gel are transferred (blotted) onto a nylon or nitrocellulose membrane.

• This makes the DNA stable and accessible for further analysis.

5. Hybridisation with Labelled Probes

• Specific VNTR or STR probes, often radioactively or fluorescently labelled, bind to complementary sequences on the DNA fragments.

• These probes highlight the areas of interest that display polymorphism.

6. Autoradiography (or Imaging)

• An X-ray film or other imaging technique is used to detect the labelled probes.

• The result is a series of distinct bands unique to each individual, known as the DNA fingerprint.

   

Dna Fingerprinting In Forensic Science 

If you want to identify a criminal at a crime scene, DNA fingerprinting will work as a means to rectify the identification of the criminal.

1. We collect DNA samples from the crime scene
2. Then we collect the DNA samples of the suspects.

From the above, we can conclude that the criminal is Suspect 2. Because Sample is matching with Suspect 2.

History of DNA Fingerprinting 

Sir William Herschel was the first to employ DNA fingerprinting as a method of identification in 1858. To identify the DNA sequences discovered between genes and identify the markers for inherited diseases so that they can be treated early, Dr. Alec Jeffreys developed the DNA fingerprinting technology at the University of Leicester in the United Kingdom in 1984.

He was unaware at the time that the same method would eventually be used to help solve murder cases or paternity trials. Later, DNA fingerprinting technology was developed in India at the CCMB (Centre for Cell and Molecular Biology), Hyderabad, by Drs. V.K. Kashyap and Lalji Singh.  Dr. Lalji Singh is the Father of Indian Fingerprinting, while Dr. Alec Jeffreys is the Father of DNA Fingerprinting.

DNA Fingerprinting Applications

The various applications of DNA Fingerprinitng are:

• Forensic Science: Biological samples such as blood, hair, saliva, sperm, and body tissue cells are used for DNA profiling. It is possible to compare the DNA recovered from the evidence sample using the VNTR (Variable number of tandem repeats) prototype. It helps in the investigation of crimes like rape and murder.
• Personal Identification: It makes use of the idea that DNA fingerprints can be used to identify people, acting as a kind of genetic bar code.
• Determining Paternity and Maternity: A person inherits their VNTRs from their parents. Cases of parentood disagreement can be resolved via parent-child VNTR prototype analysis. Additionally, immigration and inheritance proceedings may make use of this information.
• Breeding Program: Breeders typically assess a plant or animal's genotype using its phenotype. Since homozygous or heterozygous dominance is difficult to distinguish from appearance, the genotype can be determined with great care and accuracy using DNA fingerprinting. Hunting dogs and racehorses can both benefit from it.
• Diagnosis of Hereditary Disorders: It can be used to identify inherited diseases in both newborn and prenatal children. Cystic fibrosis, hemophilia, Huntington's disease, familial Alzheimer's, sickle cell anemia, thalassemia, and a host of other conditions may fall under this category.
• The creation of treatments for inherited diseases: DNA prototypes linked to the disease can be identified by examining the DNA fingerprints of family members who have a history of a particular disorder.
• Detection of AIDS: A person with AIDS can be diagnosed by comparing the HIV "RNA" band (converted to DNA via RTPCR) with the bands formed by the man's blood.