A mutation is a change that occurs in the DNA sequence of an organism. Mutations can result from errors in DNA replication during cell division, exposure to mutagens, or a viral infection. Mutations can occur in both somatic cells (body cells) and germline cells (eggs and sperm) . Germline mutations can be passed on to offspring, while somatic mutations are not passed on. Mutations can be beneficial, neutral, or harmful. They can contribute to genetic variation within species and can also be inherited, particularly if they have a positive effect. For example, the disorder sickle cell anemia is caused by a mutation in the gene that instructs the building of a protein called hemoglobin. This causes the red blood cells to become an abnormal, rigid, sickle shape. However, in African populations, having this mutation also protects against malaria. Mutations can also disrupt normal gene activity and cause diseases, like cancer. Mutations can be small-scale or large-scale. Small-scale mutations are a type of mutation where one or a few nucleotides of a gene are affected, while large-scale mutations are chromosomal mutations, such as deletion, inversion, or amplification of a region of a chromosome.