Please explain the difference between a frameshift mutation and a base substitution mutation.

A frameshift changes every codon past it. A base substitution only changes one codon.

Explanation:

DNA is comprised of nucleotides (A, C, T, G) that make up amino acids. Every three bases is called a codon and represents an amino acid.

In a frameshift mutation, a nucleotide is either added or deleted from the sequence. This offsets the entire sequence after it because the reading frame shifts. Here's an example:

ACTGCTATCGTCATC

If another T is added in between the first and second codons, then every codon after will be changed.

ACT>T<GCTATCGTCATC

A substitution mutation is usually less severe, as it only alters one codon in the sequence. These occur when one nucleotide is replaced by another one. Here's an example:

ACTGCTATCGTCATC

Let's say the first G is replaced by a T.

ACT>T<CTATCGTCATC

As you can see, none of the other codons changed.

Typically, a frameshift mutation is considered worse than a substitution mutation.