Molecular evolution

Molecular evolution pertains to changes in the DNA nucleotide sequences of the chromosomes that belong to members of a population or species. Because biologists and geneticists view such changes as underlying every heritable pertubation of the phenotypes of organisms, molecular evolution overlaps with the concept of evolution more generally. But changes even in chromosomal sequences that do not represent genes, such as in junk DNA, may be regarded as molecular evolution. Rare spontaneous errors in DNA replication give rise to the mutations that drive molecular evolution. A major debate within the scientific fields of molecular evolution and population genetics is what proportion of common mutations are neutral with respect to natural selection. Molecular evolution is the basis of the so-called molecular clock technique, which evolutionary biologists use to deduce how much time has passed since species diverged from their common ancestor, and to construct phylogenetic trees.

External Links:

[MIT History of Science http://hrst.mit.edu/hrs/evolution/public/index.html]