Genes are segments of DNA located on chromosomes. A gene mutation is defined as an alteration in the sequence of nucleotides in DNA. This change can affect a single nucleotide pair or larger gene segments of a chromosome. DNA consists of a polymer of nucleotides joined together. During protein synthesis, DNA is transcribed into RNA and then translated to produce proteins. Altering nucleotide sequences most often results in nonfunctioning proteins. Mutations cause changes in the genetic code that lead to genetic variation and the potential to develop the disease. Gene mutations can be generally categorized into two types: point mutations and base-pair insertions or deletions.