What is Homology?
In evolutionary biology, homology refers to similarities between certain structures in different organisms based on their descent from a common ancestor. An example of homology is shown in figure 1, where frogs, birds, rabbits and lizards all have different forelimbs due to their different lifestyles. However, all the forelimbs share the same set of bones, which are also seen in the fossils of their extinct common ancestor, Eusthenopteron. [1]
Different species also share homologies at the molecular level. Two genes, for example, can be related to each other by sharing a common ancestral DNA sequence. [2] Homologs consist of two subtypes called orthologs and paralogs. Orthologs are genes that result from speciation events, whereas paralogs result from gene duplication [3]. Homology can be detected and statistically measured by comparing protein and DNA sequences through tools such as Basic Local Alignment Search Tool (BLAST) and FASTA. [4].
Homologs of the Human SGSH Gene
Homo sapiens
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Drosophila melanogaster
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Mus musculus
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Rattus norvegicus
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Danio rerio
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Pan troglodytes
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fasta_updated.txt | |
File Size: | 5 kb |
File Type: | txt |
Discussion
The data using BLAST and FASTA showed that SGSH protein is highly conserved across species and has several homologs. Having this information allows us to choose from homolog model organisms to further study this gene and protein. Among the model organisms, the mouse models had the highest percent identity when compared to humans. By using other bioinformatic tools such as phylogenetics and domain analysis, we are able to use the homologies to further interpret the function of this protein.
References
[1] https://evolution.berkeley.edu/evolibrary/article/lines_04
[2]https://evolution.berkeley.edu/evolibrary/article/1_0_0/eyes_10
[3] https://schaechter.asmblog.org/schaechter/2009/03/of-terms-in-biology-ortholog.html
[4]https://blast.ncbi.nlm.nih.gov/Blast.cgi
Heather: https://www.thinglink.com/scene/650027839717900290
[2]https://evolution.berkeley.edu/evolibrary/article/1_0_0/eyes_10
[3] https://schaechter.asmblog.org/schaechter/2009/03/of-terms-in-biology-ortholog.html
[4]https://blast.ncbi.nlm.nih.gov/Blast.cgi
Heather: https://www.thinglink.com/scene/650027839717900290
This web page was produced as an assignment for Genetics 564, an undergraduate capstone course at UW-Madison.