Question: What exactly are DNA mutations and how are they formed?

Alex Holmes answered on 8 Jun 2020: last edited 8 Jun 2020 1:51 pm

Hi! So DNA is a code made up of 4 letters: A, T, G and C called “bases” and each gene is basically a long string of these bases in a particular order. In your cells, there is machinery that reads this code and then creates a protein based on it, that then goes on to do all sorts of jobs in your cell. The way the DNA is read is in sets of 3 bases, each 3 indicates a different protein building block (a bit like reading the intructions to put together furniture tells you which kind of screw or wood to use at each step).
A mutation is where a typo gets put into the DNA code: instead of atgccatagtca it might now say atgccatagtcg, so just one letter different. However, this now means when the machinery reads it, instead of making the protein it was meant to, it might now use the wrong building block and create a slightly different protein. This might not matter too much, like just making a slightly wobbly chair – it’s annoying but still works, or it could be really damaging like skipping to the end of the instructions and not making anything at all.

The way this happens is usually by random. We have machinery to proofread the DNA that usually catches these random typos and fixes them, but some might slip past. Or sometimes in cancer these proofreaders are damaged or turned off so we get more errors. Also when cells multiply their genetic material and divide, they might make mistakes that are harder to fix.

I hope that answers your question 🙂