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Identical/fraternal twin

Twin test

A DNA test can determine whether twins are identical or fraternal. The same applies to triplets.

Twin Testing

Identical (Monozygotic) Twins

Identical twins develop from a single fertilised egg that splits and forms two separate embryos. As a result, they share virtually identical DNA.

Identical twins:

  • Always have the same sex

  • Typically have a very similar physical appearance

  • Share the same genetic profile (with rare exceptions due to spontaneous mutations)

Fraternal (Dizygotic) Twins

Fraternal twins develop from two separate egg cells, each fertilised by a different sperm cell. Genetically, they are similar to ordinary siblings.

Fraternal twins:

  • Share approximately 50% of their DNA, like other siblings

  • May be of the same or different sexes

  • May, in rare cases, have different biological fathers (if two egg cells are fertilised by sperm from two different men)

Consent Requirements

All participants in a twin test must provide informed consent.

For children under 15 years of age, consent must be given by a parent with parental responsibility.

Order a Twin Test

Price: NOK 1,750 per person

Order Form: Order Twin Test from OUS (PDF)

Questions?

Please contact the us for further information and guidance.

Last updated 9/26/2025