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The key points covered in this video include:

1. DNA Profiling
2. Extraction of DNA
3. DNA Digestion
4. Producing the DNA Profile
5. Interpreting DNA Profiles

DNA Profiling

DNA profiling (or genetic fingerprinting) is a method used to produce a specific pattern of DNA bands from an individual’s genome. Every individual has a unique genome and therefore everyone has a unique DNA profile or genetic fingerprints. DNA profiling relies on short, repeating sequences of DNA that are found within the non-coding regions of DNA. These repeating sequences are called variable number tandem repeats (VNTRs). VNTRs are found in more than 1000 different locations in the human genome. In every individual, the VNTRs at each loci will differ in the number of repeats. Each individual therefore contains VNTRs that differ in length resulting in a completely unique DNA profile.

Extraction of DNA

The first stage of DNA profiling involves extracting the DNA from tissue samples. The DNA can be obtained in many different ways: DNA can be extracted from cheek cells collected by mouth swabs, DNA can be extracted from the remains of blood, hair or skin cells, Ancient DNA can be taken from inside old bones. Before DNA profiling can be carried out, the DNA must be amplified using the PCR reaction.

DNA Digestion

Once the DNA has been extracted and amplified, the DNA is digested by cutting it into small fragments using restriction endonucleases. Restriction endonucleases are a type of enzyme that cut up DNA at a specific sequence of bases called recognition sites. Specific restriction endonucleases are used to cut the DNA into fragments that leave the VNTRs intact. Since the VNTRs differ in length between individuals, the DNA fragments taken from different individuals will also differ in size.

Producing the DNA Profile
The DNA fragments are separated out by gel electrophoresis. Smaller fragments travel quicker and therefore move further along the gel. Larger fragments travel slower and therefore move less far along the gel. Gel electrophoresis produces a banding pattern that is unique to each individual. This banding pattern can be visualised by using dyes or probes that are radioactive or fluorescent.

Interpreting DNA Profiles

Once the DNA profile for each sample of DNA has been produced, different DNA profiles can be compared to each other. If the DNA profile from two different samples are the same, this suggests the DNA samples were taken from the same people. If the DNA profile from two different samples have around half the DNA bands in common, this suggests a close genetic relationship.

Summary

DNA profiling or genetic fingerprinting is a technique used to produce a specific banding pattern of DNA that is unique to each individual
DNA profiling uses short repeating sequences of DNA called variable number tandem repeats (VNTRs) to produce this banding pattern
Every individual differs in the number and length of VNTRs
Therefore, when DNA is cut into fragments that leave the VNTRs intact, the fragments will be different sizes
When these fragments are separated out by gel electrophoresis, this produces a unique banding pattern
The banding pattern can be visualised by fluorescent or radioactive DNA-binding dyes or probes
DNA profiles can be compared to each other to determine if two samples belong to the same person or a close genetic relation

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