What is STR analysis?

Here, we take a closer look at short tandem repeat (STR) analysis, how it works, and why it’s used in DNA testing.

What are short tandem repeats (STRs)?

The DNA code is made up of four nucleotide bases represented by the letters A, G, C and T.  These are the building blocks of DNA. 

Short tandem repeats (STRs) are regions of DNA where a particular pattern of letters repeats itself several times in a row. For example, one person might have a section that repeats the pattern “AGAT” – a short sequence of the DNA code made up of the letters A, G, A and T – 10 times, while another person has it 12 times.

The number of repeats is what helps make each person’s DNA unique.

Because these repeating patterns are inherited from our parents, they’re extremely useful for identifying family relationships. At each STR location, a child has two results: one inherited from their mother and one from their father.

This is why STR analysis is so effective. It looks directly at the unique combinations of repeats that make you, you.

What is STR analysis?

Short tandem repeat or STR analysis is the scientific method used in DNA testing to identify biological relationships between people. In simple terms, it’s how a DNA test compares the unique parts of your genetic code to see if you share DNA with someone else – for example, to confirm a biological father, mother, sibling, or grandparent.

Every person (except identical twins) has a completely unique DNA profile. STR analysis looks at specific areas of that DNA that are known to have patterns that repeat. By comparing these patterns, scientists can tell with exceptional accuracy whether two people are biologically related.

At AlphaBiolabs, STR analysis is the gold standard method used in all our at-home and legal DNA tests to deliver fast, accurate, and reliable results.

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How STR analysis works in DNA testing

To understand STR analysis, it helps to think of your DNA as a long string of coded information. Within that code are small sections that repeat – like tiny sequences of letters that appear multiple times in a row.

Scientists look closely at these repeating sections, known as short tandem repeats (STRs), to build a genetic profile. Everyone has STRs in the same places in their DNA (called “loci”), but the number of repeats at those places differs between individuals.

When comparing two DNA profiles – for example, from a child and a potential father – the laboratory checks these STRs side by side. Our expert geneticists look to see if the child shares one of their two results (known as “alleles”) at each STR location with the tested man. If those shared results appear across all tested locations, it provides a very strong indication that he is the biological father.

Why is STR analysis used in DNA testing?

STR analysis is widely recognised as the most reliable method for determining biological relationships. It’s the same technique used by scientists and forensic experts around the world, including in police investigations and court cases.

In DNA relationship testing, STR analysis can confirm parent-child relationships with a probability of more than 99.9% where a biological relationship exists, or can exclude the possibility of a relationship if the STRs do not match.

It’s also quick, cost-effective, and works with just a simple cheek swab, making it ideal for at-home and court-approved DNA testing.

Are STRs the same as DNA markers?

Not exactly but they are closely related.

A DNA marker is a general term for any identifiable section of DNA. Think of a DNA marker as a “point of comparison” on the genetic map.

STRs (short tandem repeats) are a specific type of DNA marker. They’re short sequences of DNA that repeat in patterns.

So, while all STRs are DNA markers, not all DNA markers are STRs. In DNA relationship testing, STR markers are the preferred type because they’re highly variable between people and easy to measure accurately.

That’s why STR analysis is the gold-standard method used by AlphaBiolabs for all DNA relationship testing – it focuses on the most informative DNA markers available.

How AlphaBiolabs uses STR analysis in our DNA tests

At AlphaBiolabs, every DNA test we perform – from paternity to sibling, grandparent, or maternity tests – uses advanced STR analysis carried out in our accredited UK laboratory.

Our cutting-edge testing equipment and expert in-house geneticists ensure your results are accurate, confidential, and delivered fast – for most of our at-home, peace-of-mind tests, this means the next business day, with a same-day option available if you need your results urgently.

What happens to your DNA sample during testing?

When you order an at-home DNA test from AlphaBiolabs, your test kit will contain everything you need to collect your DNA sample quickly and easily at home and return it to our accredited UK laboratory.

Once your sample arrives at our lab, our expert geneticists extract the DNA and prepare it for analysis.

Using advanced STR testing technology, they look for the specific repeating patterns (STR markers) in your DNA, compare them across all tested individuals, and calculate the likelihood of a biological relationship.

Your password-protected results are then sent to you via secure email, giving you answers that are clear and easy to understand.

Is STR analysis accurate?

Yes – by evaluating 25 or 45 STR markers to build a comprehensive DNA profile, STR analysis is one of the most accurate methods of DNA testing available. Because every person’s DNA profile is unique, the chance of two unrelated people having matching profiles is extremely small.

A correctly performed STR DNA test can confirm a biological relationship with more than 99.9% accuracy, making it the industry standard for all reliable DNA tests.

STR analysis vs other DNA testing methods

Other DNA testing techniques exist, such as SNP (single nucleotide polymorphism) testing, but STR analysis remains the most trusted method for DNA relationship testing.

While SNP testing is useful for ancestry or health-related DNA insights, STR analysis is far superior for paternity and broader relationship testing, because it focuses on direct inheritance patterns.

That’s why AlphaBiolabs – and most accredited laboratories worldwide – use STR analysis as the foundation of their relationship testing.

What types of DNA tests use STR analysis?

STR analysis is used in all of AlphaBiolabs’ relationship DNA tests, including:

• Paternity tests (to confirm a biological father)
• Maternity tests (to confirm a biological mother)
• Sibling DNA tests (to determine if siblings are full or half-siblings)
• Grandparent DNA tests
• Aunt or uncle (avuncular) DNA tests
• Twin testing (to determine whether two or more siblings from the same birth are genetically identical)

Every relationship DNA test uses the same trusted STR technology – giving you the same level of precision and reliability, no matter which relationship you’re testing.

Order an at-home DNA test from AlphaBiolabs

With AlphaBiolabs, ordering your at-home DNA test couldn’t be easier. Simply choose your test online, collect your cheek swab samples and home, and post them back to our accredited UK laboratory.

Our expert team performs detailed STR analysis to provide fast, accurate results you can trust – often the next business day.

Find the right test for your needs today and discover why AlphaBiolabs is the UK’s No.1 DNA testing laboratory.

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