Assessing relatedness with genetic evidence
1) DNA sequences
During the course of evolution, species undergo changes in their DNA base sequences, which accumulate until the organisms are so different that they're considered different species. More closely related species show more similarity in their DNA base sequence than those more distantly related DNA analysis has confiremd evolutionary relationships, and correct mistakes made in classication based on physical characteristics.
2) DNA hybridisation
Involves comparing the DNA base sequence of two species. To work out how closely related two species of primates are e.g humans and the chimpanzee, Pan troglodytes, DNA is extracted from both, seperated and cut into fragments. The fragments from the two species are mixed, and where they have complementary base sequences, they hybridise together. This has shown that chimpanzees and humans have at least 95% of their DNA in common, however, humans and rehus monkeys (used for animal testing) have 93% in common. (You can see how paired up the two strands are, and therefore how closely related)
3) Amino acid sequences
The sequence of amino acids in proteins is determined by the DNA base sequence. The degree of similarity in the amino acid sequences of the same protein in two species will reflect how closely related they are. Part of the fibrinogen molecule of various mammal species has been compared and the differences in the amino acid sequences have allowed scientists to propose an evolutionary tree for mammals.
The proteins of different species…