Do Twins Have Genetic Differences?

Do Twins Have Genetic Differences?

As per a study published in Nature Genetics journal, Identical twins are not as identical as previously assumed by researchers. So what makes them different? Is there a genetic variation?

Crux of the Matter

Let’s start by looking at the different combinations of placentas

Dizygotic Twins
Dizygotic or non-identical or fraternal twins are created when a woman produces two eggs at the same time and both are fertilised, each by a different sperm. The babies are no more alike than any other brothers or sisters and maybe both male, both female or one of each.

Monozygotic Twins
Also called identical twins, they occur when a single egg is fertilised then split into two (or rarely, 3 or more) creating babies with the same genes, physical features and sex. They may or may not share a placenta. Non-genetic characteristics such as size and personality can be different.

Nature v/s Nurture
Differences in identical twins were assumed to be less and studies said that it was the different environments that influenced their development like other humans. 

What Have The Researchers Found?
As per researchers at deCODE genetics, identical twins start accumulating genetic variation from the earliest stages of development i.e occur as or before embryos form.

What Does This Mean?
As per deCODE’s databases that used 381 monozygotic twin pair samples, a twin pair was found wherein one of the twins had mutations in all cells of his body, and they were not found in any cell in the body of the other twin. 

“How do we probe early human development in an ethical manner, a non-interventional manner? This is one way of doing that. We can begin to use the mutations to develop [an] understanding of how cells are allocated from the early embryo.”


  • Kodinhi is a village in Malappuram district in Kerala, India. The village came to international attention for the unusually large number of multiple births in the region. In 2008, around 30 pairs of twins from Kodinhi, along with their parents, got together to form The Twins and Kins Association, the first such association of twins in India.
  • Igbo-Ora is a city and the headquarters of Ibarapa Central, Oyo State, south-western Nigeria. The unusually large number of twin births in the region have earned the town the nickname ‘Twin Capital of the World‘.
  • A doppelgänger is a biologically unrelated look-alike, or a double, of a living person. In modern times, the term twin stranger is occasionally used.