BIOL 200 Lecture Notes - Insecticide, Omics, Transposase

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6 Apr 2012

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Naveen Sooknanan McGill Fall 2011
Gene and Genome Evolution:
Over evolutionary time, ancestral cells began to undergo differentiation which led to gene
duplication and divergence
This is because certain changes in function need to be made by the cell because of
environmental changes
For example, in the tubulin gene, divergence occurred in the ancestral cell causing the gene
product to change in structure and function.
This produced α and β Tubulin, both derived from one tubulin
This new cell the underwent divergence once more in a speciation
even to produce tubulin genes for two different species
α Tubulins 1 and 2 are found in species 1 and 2 respectively,
and have almost the same structure and function
The same applies to β Tubulin
This differentiation and speciation of an ancestral cell leads to the
production of orthologous and paralogous genes
Orthologous genes are the result of a speciation event.
They are almost identical in structure and function; the
only difference is that they are located within different
o Orthologous genes are very informative using bioinformatics and are the easiest
to compare
Paralogous genes are the result of divergence of one gene within a cell. They are different
both in structure and function, but are found within the same organism
o α and β Tubulin 1 are paralogous, because they are both located within the same
o Paralogous genes are not as informative as orthologous, and can sometimes
mislead us due to the fact that you must choose from 100s of related species
It is evident from this graph that much of the proteins found
within an organism have functions which are unknown to us
In humans, we don’t even know exactly how many
proteins there are in the body
There are various mechanisms involved in gene and genome
evolution, the most important of which are:
Genetic reassortment
Gene and segmental duplication
Exon shuffling
Control/regulatory region diversification
Domesticated transposons
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