Cystic fibrosis is caused by mutations, or errors, in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which result in either no CFTR protein being made or a malformed CFTR protein that can't perform its key function in the cell.
Insertion and deletion mutations can be as small as one nucleotide, to thousands of nucleotides long. These long insertion or deletion mutations normally occur when one part of a chromosome crosses over and changes genetic information with a different chromosome.
Sickle cell disease is a group of disorders that affects hemoglobin, the molecule in red blood cells that delivers oxygen to cells throughout the body. People with this disorder have atypical hemoglobin molecules called hemoglobin S, which can distort red blood cells into a sickle, or crescent, shape.
Substitution mutations are a type of mutation in which a single nucleotide is substituted with a different nucleotide. Examples of (base-pair) substitutions: a purine is substituted with a different purine (A → G) or a [[pyrimidine],] for a different pyrimidine (C → T).
Mutations in the HEXA gene cause Tay-Sachs disease. The HEXA gene provides instructions for making part of an enzyme called beta-hexosaminidase A, which plays a critical role in the brain and spinal cord. This enzyme is located in lysosomes, which are structures in cells that break down toxic substances and act as recycling centers.