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Biology LibreTexts

3.26: Homologies provide evidence for a common ancestor

The more details two structures share, the more likely they are to be homologous. In the 21st century molecular methods, particularly complete genome (DNA) sequencing, have made it possible to treat gene sequences and genomic organization as traits that can be compared. Detailed analyses of many different types of organisms reveals the presence of a common molecular signature that strongly suggests that all living organisms share a large numbers of homologies, which implies that they are closely related - that they share a common ancestor. These universal homologies range from the basic structure of cells to the molecular machinery involved in energy capture and transduction, information storage and utilization. All organisms:

•use double-stranded DNA as their genetic material;

•use the same molecular systems to access the information stored in DNA;

•use a common genetic code, with few variations, to specify the sequence of polypeptides (proteins);

•use ribosomes to translate the information stored in messenger RNAs into polypeptides; and

•share common enzymatic (metabolic) pathways.

Contributors

  • Michael W. Klymkowsky (University of Colorado Boulder) and Melanie M. Cooper (Michigan State University) with significant contributions by Emina Begovic & some editorial assistance of Rebecca Klymkowsky.