Mutation

a change in hereditary material, i.e. in the sequence of base pairs in the chromosomal molecules

Description
Mutations come about by copying errors during cell division, by exposure to mutagens, such as ultraviolet and ionizing radiation or chemicals, by viruses or through endogenous mechanisms, such as hypermutation (see memory lymphocyte). Germ line mutations can be passed on to offspring, while somatic mutations (of non-reproductive cells or their precursors) usually only affect the individual. A new mutation that was not inherited from either parent is called a de novo mutation. Mutations are a source of genetic variability and one of the mechanisms of evolutionary development, but are also at the heart of many diseases.

Relevance for Hemoglobinopathies
Mutations causative of sickle cell disease and thalassemia are amongst the most frequent known disease-linked genetic alterations. In particular the sickling mutation, causing an A to T transversion in the 6th codon of the human β-globin gene, and a plethora of &beta;-thalassemia and &alpha;-thalassemia mutations have been characterised functionally and epidemiologically. Because of their frequent occurrence, differences in their severity and the interaction of different mutations in mixed heterozygotes (see e.g. ), understanding the effect of the combination of different mutations for prenatal counseling is a non-trivial task.