Twin DNA test
Find out whether twins are identical or fraternal, from a cheek swab.
- Also called
- Twin zygosity test
- Answers
- Identical or fraternal
- Who takes part
- The twins, or triplets
- Samples
- Cheek swabs, at any age
- Result
- By email
How it works
Identical twins come from one fertilized egg and have the same DNA. Fraternal twins come from two eggs and share about half, like any brothers and sisters. The lab compares the twins' markers: if they match at every marker, the twins are identical.
Why parents ask
- Same-sex twins can be fraternal, and fraternal twins can look alike.
- Two placentas don't mean twins are fraternal. Identical twins can have two.
- It settles family medical history, and matters if one twin may one day need a donor.
Twins and paternity
Each twin can be tested with a possible father like any child. Standard tests can't tell identical twin men apart, so if the possible father has an identical twin, the test can't say which of them is the father.
Questions
Can newborn twins be tested?
Yes. A cheek swab works at any age.
Do boy-girl twins need a test?
No. Twins of different sexes are fraternal.
Guides for this test
- How to do a home paternity testRub a swab inside each person's cheek, let the swabs dry, seal them in labeled envelopes and mail them to the lab. The lab compares the DNA and reports whether the man is the father.
- How do you read paternity test results?Look first at the probability of paternity and the conclusion. A result of 0% means the man tested is excluded as the biological father; 99% or more, backed by a large combined paternity index, means he is very likely the father.
Other tests
- Sibling DNA test
Full siblings, half siblings or not related.
- Grandparent DNA test
When the father can't take part, his parents can.
- Aunt or uncle DNA test
When the father's brother or sister can take part.
- Maternity test
Confirms the biological mother.