UCSB Science Line
Sponge Spicules Nerve Cells Galaxy Abalone Shell Nickel Succinate X-ray Lens Lupine
UCSB Science Line
Home
How it Works
Ask a Question
Search Topics
Webcasts
Our Scientists
Science Links
Contact Information
Do twins have the same DNA?
Answer 1:

There are two kinds of twins. “Fraternal” or non-identical twins have DNA as different as any two people with the same parent. They may be the same sex or opposite sex. They may be a bit more alike than other siblings just because they grow up at the same time.

Identical twins have the same DNA (mostly). They are formed when one tiny embryo splits in two. That does not mean that the twins are really identical. Their environment is different starting off before they are even born. One twin may get more blood supply, for example. After they are born, they may have different experiences and make different choices.

There may be some differences in some of their DNA because mutations can happen at any time. So even though their DNA starts off identical, some of their cells may have slightly different DNA, you just wouldn’t know it by looking at them.

If you are interested in DNA, you may want to become a geneticist.

Thanks for asking,

Answer 2:

There are two types of twins: identical and fraternal. Identical twins, or monozygotic, come from one zygote that splits to form two embryos. Fraternal twins, or dizygotic, are a product of two separate eggs being fertilized. Identical twins are usually both boys, or both girls, but fraternal twins can be both boys, both girls, or even a boy and a girl. Identical twins, since they are split into two from the same zygote, can have the same DNA. The DNA isn't perfectly identical, but it's pretty similar. They look almost exactly the same, but each twin develops and lives their life separates so they are exact mirror images of each other. Fraternal twins, obviously, would have a greater difference in DNA because they are already to completely separate eggs that are being fertilized to become two completely separate babies. So, basically identical twins have "similar" DNA and fraternal twins do not.


Click Here to return to the search form.

University of California, Santa Barbara Materials Research Laboratory National Science Foundation
This program is co-sponsored by the National Science Foundation and UCSB School-University Partnerships
Copyright © 2015 The Regents of the University of California,
All Rights Reserved.
UCSB Terms of Use