eli5 how does DNA mutate? and why?


My mom is listening to me rattle off answers from you guys and wanted to ask one herself! Thanks for your participation!

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DNA copy is not 100% exact, a bit like when you xerox a document over and over and over again.

Sometimes there is no error. Sometimes the error does not matter. Sometimes the error breaks something and the new DNA is so wrong the cell cannot survive. Sometimes the new DNA is actually an improvement.

Through billions of trial and error, those improvements have caused evolution.

To understand DNA mutations, you have to have a bit of an understanding of what goes on inside of a cell.

The DNA is located inside the nucleus of the cell and acts like the “master blueprint” for making proteins, which are the functional aspects of our body. If you were building a skyscraper, you wouldn’t want the crucial blueprints to be altered or damaged, right? So what do you do? You keep the blueprint locked away, and anything going out to the site is a copy of the original. The body does this as well, and the “copy” that is read by ribosomes to build the protein sequence is called “messenger RNA,” or mRNA.

Now, there’s a few different types of mutations.

“Point mutations” occur when a single member of a base pair (A and T pair with C and G) is substituted for something else. Because the blueprint is wrong, the resulting build is wrong: it’s like the blueprint for the skyscraper instructing a wall to be built with wood, but instead, the instructions were changed to plastic.

“Insertions and Deletions” are also referred to as “frameshift mutations” because there are certain sequences of base pairs that tell the ribosome that the reading of the mRNA strand is complete. Deleting or inserting base pairs can throw off the position of this “stop sequence,” leading the ribosome to either add too many or not enough amino acids to the chain. It’s like the construction crew editing the blueprint and accidentally pasting the “materials needed” for plastering into the foundation section and not knowing any better that they don’t belong.

There are many reasons why mutations occur. Sometimes it’s as simple as the processes that regulate them aren’t, and can’t always be, 100% perfect all of the time. Other times, DNA regions get damaged by environmental factors such as cigarette smoke or UV radiation, and the repair wasn’t sufficient.