Mosaicism: When You Have Two DNA sets in Your Body

We were born different from one another. It doesn’t matter if you have an identical twin or you look like the younger version of your parents. There will always be something different in your physical appearance, personality or interests that set you apart from them.

But apart from that, there’s also a strand inside our bodies that set us apart from everyone. We call that strand a DNA. A DNA is like a fingerprint, it gives us our own identity that is different from everyone else. No DNA strand is exactly alike. But one can use their DNA for checking biological information like checking if you’re a criminal based on a strand of hair found at a crime scene or if you’re the missing child of  a couple.

But what if there’s more than one set of DNA in your body? Is that possible? And if yes, how does it happen? The answer, Mosaicism.

Mosaicism happens when you have more than two DNA sets in your body. In a way, this can be similar to chimeras (organisms who have two DNA sets in their body when they absorbed their twin during fertilization and development in the mother’s womb).

Mosaicism on the other hand occur in organisms who came from a single zygote. They did not absorb their twin but still end up with more than one set of DNA in their bodies. This happens during the early stages of development of the baby in the womb. During the division process of the cells (some of which occurs very rapidly), some of the cells get confused and do not replicate their DNA properly. One of the cells mutate unnoticed, and replicates a different DNA than that of the other cells. But these cells with a different DNA is still inside the baby.

If the mutation is not too serious, the baby will be born with a trait seen in some cells but not in the others. One example of mosaicism can occur in cats. The eyes of the cat have two different colors.

Sometimes, mosaicism can affect skin cells. The skin will have two or more different colors, resembling a mosaic painting as shown below.

Mosaicism in skin cells also follow a certain pattern. Some of these patterns are shown below.
The world of genetics is still too big. There are still areas and other possibilities that have not been explored yet. Some questions still remain unanswered. Is cloning possible in humans or does having mosaicism makes it difficult to know what your DNA strand really is?

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