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The Science Behind: Twins (cover- Sara Chaudhari)

Updated: May 2, 2020

Have you ever seen twins so identical, that you think they’re the same person? Have you ever wondered why that happens? Why twins even occur?

In reality, there are actually seven types of twins:

  • Mirror Image Twins

  • Half-identical Twins

  • Mixed chromosome twins

  • Superfetation

  • Superfedunctation

  • Fraternal

  • Identical

Our focus in this article will mainly be about what makes twins identical or not. Leave a comment or a suggestion if you would like an article about the other types of twins as well.

Twins are known to be rare. in fact, they only used to make up about 2% of the world’s population, however, with technologies such as IVF rising, it is possible for more twins to be born.

The two types of twins we’re going to talk about are Monozygotic (identical twins) and Dizygotic (non-identical-twins).

Twins have been a fascinating topic of study for scientists for decades. Studying twins help up better understand how the environment plays a role in human life.

Monozygotic: These are identical twins. These types of twins occur when one fertilized egg splits into two within 14 days of fertilization. If this phenomenon occurs after 14 days, the twins are conjoined (Siamese twins)

It is not known why an embryo splits into two. It is a random event. Thanks to IVF it is possible to artificially split embryos, increasing the rate or Monozygotic twins.

Though Monozygotic twins share the same DNA, they are not the same person. They might have slight differences in looks, personality, and behavior. These differences are caused by the babies’ genetic make-up and environmental differences from the moment they start forming. This is why one twin might be bold and the other timid, even if they look the same!

Dizygotic twins: These are non-identical or fraternal twins. These twins occur when instead of one egg being fertilized there are two. These two eggs will not have the same DNA, but a similar one. It’s like how some siblings look alike regardless of their ages. Unlike monozygotic twins, dizygotic twins are not random. Certain cultures have higher rates of giving birth to Dizygotic twins. Hyper-ovulation(releasing two or more eggs at one time) is a hereditary trait.

Twins are a very interesting phenomenon. Scientists are not yet clear if their traits are more affected by nature or genetics. Being able to properly study the effects of the environment and genetics on twins might also be able to help cure complex diseases!!

Next time you see a pair of twins, try to guess which one of the seven types they are!

Until then...

Stay Curious ;)






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