Download Molecular Phylogeny

Molecular Phylogeny
In 1859 Charles Darwin provided a mechanism called natural selection, that could explain how
evolution occurs. Darwin's theory of natural selection helped to convince most people that life has
evolved.
Darwin's book "The Origin of Species by Means of Natural Selection" summarized all of the evidence in
favor of the idea that all organisms have descended with modification from a common ancestor. Darwin
also advocated natural selection as a mechanism of evolution. Biologists no longer question whether
evolution has occurred or is occurring. However, the MECHANISM of evolution is still debated.
During the first part of this century the incorporation of genetics led to an understanding of the
importance of mutation and variation within a population. Natural selection then became a process that
altered the frequency of genes in a population and this defined evolution.
It must be remembered that Darwin was unaware of genes and Mendelian genetics when he published
his findings. The modern theory of the mechanism of evolution differs from Darwin's concept in three
important aspects:
1. It recognizes several mechanisms of evolution in addition to natural selection. One of these, random
genetic drift, may be as important as natural selection.
2. It recognizes that characteristics are inherited as genes. Variation within a population is due to the
presence of multiple alleles of a gene.
3. It postulates that speciation, the creation of a new species, is (usually) due to the gradual accumulation
of small genetic changes.
In other words, Mendelian genetics answers questions about how evolution works at the level of genes,
phenotypes, and populations whereas Darwinism was concerned mainly with organisms, speciation and
individuals.
DNA analysis techniques are used to determine the relationship of organisms and from which organism
they evolved. A new field called Molecular Phylogeny has developed to trace these relationships.
What is Molecular Phylogeny?
Molecular phylogeny is the inference of lines of
ancestry for organisms based on DNA, RNA, or
protein sequences. The primary assumption in all
phylogenetic analyses is that all organisms are
actually related, and that the real problem is that of
determining just how close or distant the
relationship is.
What is the mechanism for change in DNA?
The main mechanism for change is the occurrence
of point mutations that occur over time. These
may be deletions or insertions combined with
substitutions that alter the amino acid sequence of
a protein.