How to Compare Two Genetic Profiles? A Complete Guide with Practical Examples
- Info Test ADN
- Aug 2
- 4 min read
Comparing genetic profiles helps answer essential questions: Are we biologically related? or Does this sample contain my DNA?
In this article, discover how DNA comparison works, whether it’s to confirm paternity or maternity or verify if a sample belongs to you.
What is a genetic profile?
A genetic profile is a biological identity card created from your DNA. It is based on the analysis of genetic loci (specific areas of the genome).
Each locus contains two alleles:
One inherited from the father
One inherited from the mother
In short: your genetic profile is a table listing the pairs of alleles that make up your DNA.
1. Comparing two genetic profiles to confirm a biological relationship
The most common case is the paternity or maternity test. It involves verifying whether a child shares their alleles with an alleged parent.
How does it work?
Each child inherits 50% of their DNA from their father and 50% from their mother.
When comparing the DNA of a child to that of an alleged father, at least one allele must match at each analyzed locus.
Simplified example:
Locus | Child | Mother | Father |
D3S1358 | 15 - 17 | 15 - 16 | 17 - 18 |
vWA | 14 - 18 | 14 - 17 | 18 - 19 |
nterpretation:
At locus D3S1358, the child has 15 and 17. The 15 comes from the mother, the 17 from the father.
At locus vWA, the child has 14 and 18. The 14 comes from the mother, the 18 from the father.
If all loci show a match with the tested father, paternity is confirmed (with a probability often >99.99%).
If several loci do not match, paternity is excluded.
2. Comparing two genetic profiles to verify a sample
Genetic profile comparison can also be used to verify whether an object or recovered sample contains your DNA. This is particularly useful when you want to know if an object belongs to you, if it was used by you, or even for certain private investigations.
Practical example:
You find an object – such as a toothbrush, tissue, piece of clothing, hair with root, or even fabric with biological traces – and want to know if it contains your DNA.
This procedure involves several steps:
1. Object analysis
First, you must send the recovered object to the laboratory.
The laboratory will perform DNA extraction from the item (if possible).
From this DNA, it will create a complete genetic profile.
Note: This step is not always successful. The quality and quantity of DNA will depend on:
The type of sample (hair, fabric, dried saliva, etc.)
The state of preservation (recent or old object, exposure to heat, humidity, etc.)
The support material (some surfaces do not retain DNA well)
If extraction is successful, the laboratory will provide a genetic profile of the DNA found on the object.
2. Reference test
Next, you must provide a reference sample:
Most often, this is a saliva swab collected using a buccal swab (a cotton swab rubbed inside the cheek).
In some cases, other types of samples may be used (hair, nails, etc.).
The laboratory will analyze this sample and provide you with your own genetic profile, established separately.
3. Comparison of the two profiles
Finally, the two genetic profiles – the object’s and yours – are compared locus by locus.
If all loci match perfectly, this means that the DNA extracted from the object is indeed yours.
If differences appear at several loci, then the DNA found on the object is not yours.
It is essential that the comparison be complete: a genetic profile is considered identical only if all analyzed loci are the same.
This two-step approach (object profile + reference profile) provides a clear and reliable answer.
Legal and ethical issues related to sample analysis
It is important to remember that analyzing a biological sample cannot be done freely without complying with certain legal and ethical rules.
In many countries, it is illegal to perform a DNA test on a person without their consent. This means that if you find an object potentially containing someone’s DNA (toothbrush, tissue, hair, etc.), you cannot legally request analysis of this DNA without the person’s consent.
What are the risks?
Having someone’s DNA analyzed without their knowledge may be considered an invasion of privacy and may hold you liable.
Using this type of genetic profile in a judicial or administrative procedure could be challenged, or even expose you to penalties.
Precautions to take:
Always clearly declare to the laboratory the origin of the sample and the purpose of the analysis.
Do not retain the genetic profile if it does not belong to you. You can request the laboratory to immediately destroy the results if necessary.
Use this type of analysis only in a private and non-judicial context, unless an attorney or judge has advised you to do so.
FAQ – Frequently Asked Questions
1. Can two genetic profiles be compared without a laboratory?
No. Specialized equipment and scientific expertise are required.
2. How long does it take to get results?
On average 3 to 10 business days.
3. Can old or degraded samples be analyzed?
Yes, often, but success depends on their preservation state.
4. Are these analyses reliable?
Yes. With the analysis of 15 to 25 loci, the probability of error is almost zero.
5. Can these analyses be used in a legal context?
Yes, but this requires a legal DNA test, regulated by law, with official participant identification.