READ: Evidence for Evolution
8. Molecualr Evidence
Similarities Between Molecules and Genomes
Molecular Clocks
Arguably, some of the most significant evidence of evolution comes from examining the molecules and DNA found in all organisms. The field of molecular biology did not emerge until the 1940s and has since confirmed and extended the conclusions about evolution drawn from other forms of evidence. Molecular clocks are used in molecular evolution to relate the time that two species diverged to the number of differences measured between the species' DNA sequences or protein amino acid sequences. These clocks are sometimes called gene clocks or evolutionary clocks. The fewer the differences the less time since the divergence of the species. For example, a chicken and a gorilla will have more differences between their DNA and protein amino acid sequences then a gorilla and an orangutan. This provides additional evidence that the gorilla and orangutan are evolutionally closer related than the gorilla and the chicken.
Molecular clocks, combined with other forms of evidence, such as evidence from the fossil record, have provided considerable evidence to estimate how long ago various groups of organisms diverged evolutionarily from one another.
Almost all organisms are made from DNA with the same building blocks. The genomes (all of the genes in an organism) of all mammals are almost identical.
Molecular Genetics
The development of molecular genetics has revealed the record of evolution left in the genomes of all organisms. It also provides new information about the relationships among species and how evolution occurs.
Molecular genetics provides evidence of evolution such as:
- the same biochemical building blocks – such as amino acids and nucleotides - are responsible for life in all organisms, from bacteria to plants and animals
- DNA and RNA determine the development of all organisms
- the similarities and differences between the genomes, the gene sequences of each species, reveal patterns of evolution.
This is a map of the genes on just one of the 46 human chromosomes. Similarities and differences between the genomes (the genetic makeup) of different organisms reveal the relationships between the species. The human and chimpanzee genomes are almost identical- just about 1.2% differences between the two genomes. The complexity of the map signifies close evolutionary relationships when the genomes are highly similar.
CK-12 Foundation, Biology. http://creativecommons.org/licenses/by-nc-sa/3.0/