What is Homology?
Homology refers to the similarity that is present between the structures, physiology, and/or development of different species as a result of sharing a common evolutionary ancestor. A widely used example of homology is the forelimb bone structures of vertebrates; though taking on different shapes and forms from adaptation to different environments and modes of life, the general form and number of bones in the forelimbs of varying vertebrates have remained practically identical. [1] This idea of homology can also be applied to the smaller, basic building blocks of life: genes, transcripts, and proteins. When applying homology to genes, there are two different classification of homologous genes: orthologs and paralogs. Orthologs refer to genes that result from speciation while Paralogs refer to genes that arise from gene duplication events. [2]
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FOXE1 Homologs
FOXE1 is a highly conserved gene encoding for the FOXE1 protein: a transcription factor that is believed to play a central role in thyroid morphogenesis. [3] As the structure of the FOXE1 gene is highly conserved (up to 89% between humans and mice), studying the gene function and mechanism of FOXE1 homologs may provide valuable insight into ways in which thyroid related diseases can be treated.
Macaca mulatta (Rhesus Monkey)
FOXE1 Accession Number: XP_014972717.1 Length: 372 AA Percent Identity: 97% |
Xenopus tropicalis (Xenopus)
FOXE1 Accession Number: XP_002936729.1 Length: 377 AA Percent Identity: 49% |
Discussion
The percent identity of a gene is a measurement of the similarity between the DNA sequences of the gene and a reference gene (in this case the human FOXE1 gene). [4] The high percent identity of the mammalian FOXE1 homologs shows that FOXE1 is highly conserved across species and likely plays an important role in the physiological functions of these organisms. Not only that, the relatively high percent identity of the Coelacanth suggests that the FOXE1 gene (or its precursor) likely originated a long time ago and was conserved throughout evolutionary history due to its importance in regulating physiological functions.
References
[1] Britannica, The Editors of Encyclopaedia. “Homology.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 8 Sept. 2016, .https://www.britannica.com/science/homology-evolution
[2] Jackson, Julius H. “Gene Similarity: Some Definitions.” Michigan State University, https://msu.edu/~jhjacksn/Reports/similarity.htm
[3] De Felice, M., Ovitt, C., Biffali, E., Rodriguez-Mallon, A., Arra, C., Anastassiadis, K., Macchia, P. E., Mattei, M.-G., Mariano, A., Scholer, H., Macchia, V., Di Lauro, R. A mouse model for hereditary thyroid dysgenesis and cleft palate. Nature Genet. 19: 395-398, 1998. Retrieved from https://www.nature.com/articles/ng0898_395
[4] Percent Identity of Genomic DNA and Amino Acid Sequences. CARTA. Retrieved from https://carta.anthropogeny.org/moca/topics/percent-identity-genomic-dna-and-amino-acid-sequences
[1] Britannica, The Editors of Encyclopaedia. “Homology.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 8 Sept. 2016, .https://www.britannica.com/science/homology-evolution
[2] Jackson, Julius H. “Gene Similarity: Some Definitions.” Michigan State University, https://msu.edu/~jhjacksn/Reports/similarity.htm
[3] De Felice, M., Ovitt, C., Biffali, E., Rodriguez-Mallon, A., Arra, C., Anastassiadis, K., Macchia, P. E., Mattei, M.-G., Mariano, A., Scholer, H., Macchia, V., Di Lauro, R. A mouse model for hereditary thyroid dysgenesis and cleft palate. Nature Genet. 19: 395-398, 1998. Retrieved from https://www.nature.com/articles/ng0898_395
[4] Percent Identity of Genomic DNA and Amino Acid Sequences. CARTA. Retrieved from https://carta.anthropogeny.org/moca/topics/percent-identity-genomic-dna-and-amino-acid-sequences
Image References
[1] https://cpb-ap-southeast-2-juc1ugur1qwqqqo4.stackpathdns.com/blogs.auckland.ac.nz/dist/0/134/files/2010/11/17-Homology-of-terrestrial-mammallian-forelimbs-No-Title.jpg
[1] https://cpb-ap-southeast-2-juc1ugur1qwqqqo4.stackpathdns.com/blogs.auckland.ac.nz/dist/0/134/files/2010/11/17-Homology-of-terrestrial-mammallian-forelimbs-No-Title.jpg