The genomes

5. Comparing genomes

One of the most interesting new fields that the availability of the complete genomes has created is the science of genome comparison. Comparing complete genomes can give deep insights about the relationship between organisms, as well as shedding light on the function of specific genes in each single genome. It is clear that this field has just begun, and that there are many discoveries waiting to be made.

Some examples of issues that have been investigated to some degree:

It is now possible to investigate which sets of genes are common to many different organisms, or groups of organisms. Is there a common core of genes necessary for all life? Is that core sufficient for life?
If one looks at a specific, and yet fundamental, component such as the ribosome and the protein synthesis, can one say anything about whether this system has changed fundamentally through evolution, or has it stayed basically the same throughout? Have there been inventions during evolution in such a fundamental system?
Which genes are necessary for multicellular life forms; which set of genes are only found in multicellular organisms but not in unicellular ones?
The rate of horizontal gene transfer (genes that have jumped the species barrier) among bacteria can now be investigated. How often, and under what circumstances do bacteria exchange genes? Has anything similar happened with higher organisms?
Where and how have new genes emerged in evolutionary history? Can precursors of some gene families be found in distant relatives of a species?
The problem of identifying and characterizing orthologous genes versus paralogous genes becomes easier to address (but not necessarily solve).
- Orthologues are genes that have diverged from a common ancestor because of a speciation event.
- Paralogues are genes that have diverged as the result of a gene duplication event.
Warning: The term orthologous and paralogous are sometimes used to denote functional equivalence, and similarity without functional equivalence, respectively, but this is frowned upon by evolutionary biologists.