What Is Y-STR DNA?
When it comes to genetic material, all of us share 99.9% of DNA. It’s the 0.1% difference that leads to three million variations between humankind. These differences come from the regions of the genes inherited from parents. For example, the Y chromosome is passed down from the father and remains unchanged for generations.
Here’s a video explaining how the Y chromosome is passed down from father to son:
The short tandem repeats on the Y chromosome are microsatellites, Y Chromosome STR, or Y-STR. This repeats in varying numbers by the individual. Y-STR analysis is effectively a comparison between two males in areas such as forensics and genetic genealogy.
The gist of Y-STR profiling is that two unrelated people have a slim chance of sharing the same repeated sequence. The probability becomes even narrower when you magnify the scope of analysis.
What Information Can Y-STR DNA Reveal?
Y-STR DNA testing is conducted on the short repeating sequences of the male genetic material and not the female equivalent. Moreover, every testing laboratory has its unique terminology and technical jargon when it comes to results.
Take a look at the attributes revealed in such a test.
- Patrilineal relations: From father to son, grandparents, cousins, and any other unbroken male line
- Marker levels and value: Name of the marker on the Y chromosome by segment, levels (12, 25, 67, 111), its length, and repeat structure
- Familial matches: Depending on the service you use to test your DNA, you’ll be shown matches from its library to relatives and families
- Y-DNA haplotype and haplogroup: The repeated sequences on specific markers on the Y-STR DNA is the haplotype. The segment of people with the most recent common ancestor (MRCA) dating back to hundreds and thousands of years is the haplogroup
- Surname matches: Paternal matches with different surnames may come out with your test results. This way, you can communicate or connect with those who match your surname and genetics
- Migratory routes of ancestors: Depending on the algorithm you use, the computed migratory map of your ancestors may be revealed based on references from other genetic references in the library
How Does Y-Chromosome Testing Work?
There are two ways to perform the Y-STR testing, legal and non-legal, just like in a mitochondrial DNA test.
The first method refers to a setup where a third-party official such as your doctor oversees the complete happenings. Such a setup is to prevent malaise and cheating on the test. The non-legal Y-STR analysis can be conducted at your home or the clinic, based on your preferences. In either case, this is what happens:
- You prepare the mouth by avoiding smoking and drinking coffee or tea for three to four hours before the test
- Sterile cotton or buccal swab per person to collect epithelial cells from the cheeks
- The sample is submitted to your doctor (for legal testing) or sent back to the testing authority via prepaid mail as instructed
If the physical locations of both the males you want to test are different, at-home DNA testing companies even ship multiple kits to all the parties at nominal extra costs.
Use Of Y-STR DNA In Forensics
When it comes to Y-STR forensic analysis, the same method has been used since 1990 for a variety of things like paternity and ethnicity DNA testing. This tried-and-true method remains the same because men are involved in 80% of all violent crimes and 95% of all sexual offenses.
When DNA is split between parents during conception, a man receives an almost-identical Y chromosome from his father. This is why genetic material found on a crime scene can reveal the culprit and rule out the innocent if an assailant’s patrilineal DNA is present in the database already. It can also help in cracking cold cases.
For example, take the murder of 16-year-old Marianne Vaatstra on May 1st, 1999. Police in the Netherlands searched for 14 years for the man who raped, strangled, and killed her, until they found the culprit via Y-STR testing.
In the same way, this analysis can reveal the assailant in cases such as one with a female victim and male assailants or one where only the genetic material of the kin of the culprit is available. Also, it’s useful when there’s only a minimal amount of male DNA available, an admixture, or no spermatozoa.
Forensics can use the same type of test to resolve paternity disputes easily because close relations show zero to two differences in their Y-STR test. The test is crucial for finding missing males as well as in the identification of male disaster victims. Domestic violence cases can be proven using intimate swabs or body swabs besides analyzing clothing items.
Y-STR acts as a backup to autosomal testing and helps in finding multiple male criminals, if applicable.
Genetic DNA Testing In Short
Genetic testing isn’t limited to Y-STR analysis alone. There are several more options available, such as mitochondrial DNA analysis, for exploring the matrilineal heritage. When it comes to autosomal testing, both paternal and maternal lineages are reported in results.
Beyond details pertaining to lineage, genetic testing is among the best ways to understand more about your ethnicity, such as if you have African, European, Asian, American, or Jewish ancestry. It reveals your ethnicity mix in percentages by comparing your genetic sample with that of the available reference library. Also, it’s a reliable marker of health since it can reveal predispositions to over 2,000 hereditary diseases.