Refers to mistakes made when chromosomes are being replicated (e.g., deletion of certain genes or making too many copies of certain genes). They can give rise to mutations during cell division and DNA replication, and as such are one of the prime movers of genetic changes that drive evolution. Some errors such as in a gene nucleotide sequence that controls basic cell design or oxygen transport are lethal and are almost immediately ‘selected out’ so that they are not inherited by descendants. Copying errors can also be induced by environmental agents such as cigarette smoke, radiation and sunlight, but these are not passed on to descendants. Those that do occur in the DNA of cells that produce the egg and sperm, and which result in germ line mutations that give rise to hereditary diseases.
See Chromosome, DNA (deoxyribonucleic acid), Genetic (or DNA) recombination, Mosaicism, Mutation (biology), Nucleotide, Theory of natural selection