What are the two types of DNA mutations?

1 Answer
Mar 17, 2018

Deletions and insertions.


There are actually three, but I'll describe these two because they tend to be more impactful in terms of an effect on the actual genetic sequence.

Deletion: exactly what it sounds like. A nucleotide is essentially just taken out of the DNA sequence. This is pretty impactful because it completely changes the order of the sequence. I can make an analogy to a sentence:
"Hello how are you?"
If I delete the first letter:
"Elloh owa rey ou?"
DNA works in sequences of three nucleotides, which is comparable to the spaces in the sentence. Just deleting one letter completely changed it.

Insertion: Inserting a nucleotide into a sequence. I'll do the sentence thing again:
"Hello how are you?"
If I insert a letter into the sentence but keep the spaces the same:
"Hello who war eyo u?" (I inserted a "w" before the word "how").

Both of these are especially impactful because if the order of a DNA sequence changes, often the stop codon that ends the sequence will not exist anymore, and a new stop codon will emerge earlier in the sequence or much later in the DNA strand.

A third is substitution, where one nucleotide gets replaced by another. Since you can make the same codon with multiple sequences of nucleotides, this often actually has no impact on a DNA sequence, or it only changes one part of it, but doesn't drastically impact the protein that the DNA will make.