How does a change in DNA sequence affect a proteins function

A missense mutation is a mistake in the DNA which results in the wrong amino acid being incorporated into a protein because of change, that single DNA sequence change, results in a different amino acid codon which the ribosome recognizes. ... More frequently, it causes the protein to be less effective in doing its job.

because it can change who you are ,

ok yes, but what is the question? as soon as you ask the actual question i will answer it. : )