DNA is our identity. It’s our code. It’s why our cells are able to work. It is the foundation for who we are. It’s what makes us who we look like. It’s why you have yellow hair and brown eyes. It’s why you tan more easily than your brother.

DNA is shaped like a ladder. The rails of the ladder are made up by phosphate and sugar. There are four chemicals in the middle that make up the rungs of the ladder:

  1. Adenine
  2. Thymine
  3. Guanine
  4. Cytosine

Adenine is always attached to Thymine and Guanine is always attached to Cytosine. That is the rule. Like this:

dna-ladderThe four letters correspond to the four chemicals.

But you don’t just have a straight ladder lying in the nucleus of all your cells. The ladder is twisted.


Cell reproduction is called mitosis. In mitosis, the cell splits its DNA in half, creating two DNAs. The cell then splits itself (in the most basic term of mitosis), creating two new cells.

In order to be split to create two DNAs, the ladder untwists itself. Once it’s untwisted, special enzymes called DNA polymerases pull at the rails of the ladder, separated the four chemicals from each other. Immediately a new thymine jumps onto a separated adenine or a guanine jumps onto a separated cytosine, and vice-versa. A new rail is formed of more phosphate and sugar and there you are! Two beautiful new DNAs ready to perform at their very best inside the nucleus of the cell.


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