Answer by 4Megan.Oneil. Confidence votes 94. A small change in a person's DNA cause a genetic disorder because changes in a gene's DNA sequence can change the organisms proteins by altering their amino acid sequences, which may directly affect one's phenotype which most likely would result in a genetic disorder.erge this question into. Split and merge into it. Answer by 4Megan.Oneil. Confidence votes 94. A small change in a person's DNA cause a genetic disorder because changes in a gene's DNA sequence can change the organisms proteins by altering their amino acid sequences, which may directly affect one's phenotype which most likely would result in a ...