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Linné on line arrow Plants and Animals arrow The order in nature arrow DNA reveals relationships

DNA reveals relationships

Coffee plant.
Photo: Fredrik Karlsson.
  When two sex cells meet and are united they form a new cell and the new life begins. This first cell looks very similar in all species. After a while it develops into a specific organism, for instance a rabbit or a camel. The information in the cell's DNA directs the development of the cell. A rabbit's DNA tells that the rabbit should have long ears and a short tail but no humps on the back.

Cells build up all living things. In each cell there is DNA in long threads with shorter regions called genes. The DNA is inherited from generation to generation but can also change by chance. Changes in DNA are the bases for evolution and the origin of new species.

A new way to find out what species are most closely related is by comparing DNA with modern methods. The ideal situation would be to be able to compare all DNA, but this is too expensive and time consuming. Therefore only one or a few genes are compared when trying to show relationships. The ”building bricks” of the genes (DNA) can be separated on a gel where they are shown as bands.

The DNA from the coffee plant is seen as a pattern of bands on a gel.
Photo: Katarina Andreasen

To show how the species are related to each other, an evolutionary tree (cladistic tree) can be made by comparing the sequences of ”building bricks” in the DNA from the species studied. Such a tree most often gives the clearest information about relationship among species.