Such conditions, it is argued, are readily distinguishable from genetic diseases associated with increased mortality, but not associated with an aging phenotype, such as cystic fibrosis and sickle cell anemia. It is further argued that segmental aging phenotype is a natural part of aging insofar as genetic variation leads to some people being more disposed than others to aging-associated diseases such as cancer and Alzheimer's disease. DNA repair defects and increased cancer risk Individuals with an inherited impairment in DNA repair capability are often at increased risk of cancer. When a mutation is present in a DNA repair gene, the repair gene will either not be expressed or be expressed in an altered form. Then the repair function will likely be deficient, and, as a consequence, damages will tend to accumulate. Such DNA damages can cause errors during DNA synthesis leading to mutations, some of which may give rise to cancer. Germ-line DNA repair mutations that increase the risk of cancer are listed in the Table. See also Biogerontology Degenerative disease DNA damage theory of aging Genetic disorder Senescence References External links BRCA - Companion Reviews and Search Terms BRCA1 - Companion Reviews and Search Terms BRCA2 - Companion Reviews and Search Terms ATM - Companion Reviews and Search Terms NBS1 - Companion Reviews and Search Terms Bloom s syndrome - Companion Reviews and Search Terms Fanconi s anemia - Companion Reviews and Search Terms WRN - Companion Reviews and Search Terms RECQ- Companion Reviews and Search Terms RECQL4 - Companion Reviews and Search Terms FANCJ - Companion Reviews and Search Terms FANCM - Companion Reviews and Search Terms FANCN - Companion Reviews and Search Terms XPB - Companion Reviews and Search Terms XPD - Companion Reviews and Search Terms XPG - Companion Reviews and Search Terms MSH6 - Companion Reviews and Search Terms MUTYH - Companion Reviews and Search Terms DNA repair and toxicology - Companion Reviews and Search Terms Neoplasia inherited - Companion Reviews and Search Terms Neoplasia carcinogenesis - Companion Reviews and Search Terms Segmental Progeria Cancer DNA repair Mutation DNA replication and repair-deficiency disorders Causes of conditions Senescence