This website was constructed as a class project for Genetics 564, an undergraduate Genetics course at UW-Madison.
What is Homology?
Homology is physiological, genetic, or developmental similarity between species based on a shared common ancestor [1]. Species that have homologous genes to human genes are important in medical and genetic research. Individual nucleotide sequences can be compared in NCBI BLAST, an online tool that analyzes genes and proteins for homology between species. It aligns the sequences and calculates the degree of overall similarity. Since experimenting on humans is unethical in most cases, scientists frequently use NCBI Blast to find model organisms that may be suitable for researching a gene of interest. If a gene is shared between a large number of species, this may indicate its relative importance to the species' biological functions [2].
Aldolase B Gene Homology
The Aldolase B gene is conserved among many species. It is shown below in six species, five of which are commonly used model organisms. While the Aldolase B gene nucleotide sequence is not completely identical in each organism, its percent identity match is shown in the diagram below. It also has the same function in all of the species listed below, so it can be considered an orthologous gene. Orthology is homology in genes that also retain the same function over evolutionary time [3]. The process of glycolysis is well-conserved among species because it is important for metabolism [4]. Species that share a gene that has the same function are known as orthologous species. All of these organisms have what is considered by NCBI standards a high degree of genetic similarity for the Aldolase B gene, and could all theoretically be used for studying aldolase B. Humans and chimpanzees only differ by 1%, which is unsurprising given how closely related the two genomes are overall [5]. Mice, the only other mammalian model listed here, also shares a high degree of genetic similarity within the Aldolase B gene. What is perhaps most interesting about Aldolase B homology among the six organisms listed is how similar they are despite significant morphological differences; the sequence is conserved between species as different as humans and nematodes. This universality speaks to Aldolase B's biological importance.
Reference Sequences
Human:
Accession Number: NC_000009.12 FASTA Gene name: ALDOB Chimpanzee: Accession number: XM_001136159 FASTA Gene name: ALDOB |
References
1. Encyclopedia Britannica. (2014). Homology (evolution). Retrieved March 6, 2014, from http://www.britannica.com/EBchecked/topic/270557/homology.
2. Koonin EV, Galperin MY. Sequence - Evolution - Function: Computational Approaches in Comparative Genomics. Boston: Kluwer Academic; 2003. Chapter 2, Evolutionary Concept in Genetics and Genomics. Available from: http://www.ncbi.nlm.nih.gov/books/NBK20255/
3. Lewis, C. Definition of Homolog, Ortholog, and Paralog. Retrieved March 6, 2014, from http://homepage.usask.ca/~ctl271/857/def_homolog.shtml.
4. NCBI Bookshelf. (2000). The Origin and Evolution of Cells. Retrieved May 18, 2014, from http://www.ncbi.nlm.nih.gov/books/NBK9841/.
5. Hopkins, W.D., Lyn, H., Cantalupo, C. (2009). Volumetric and Lateralized Differences in Selected Brain Regions of Chimpanzees (Pan troglodytes) and Bonobos (Pan paniscus). The American Journal of Primatology. 71(12): 988-997. doi: 10.1002/ajp.20741 Retrieved May 18, 2014, from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2804891/
Gene homology diagram created by Maddy Ford
2. Koonin EV, Galperin MY. Sequence - Evolution - Function: Computational Approaches in Comparative Genomics. Boston: Kluwer Academic; 2003. Chapter 2, Evolutionary Concept in Genetics and Genomics. Available from: http://www.ncbi.nlm.nih.gov/books/NBK20255/
3. Lewis, C. Definition of Homolog, Ortholog, and Paralog. Retrieved March 6, 2014, from http://homepage.usask.ca/~ctl271/857/def_homolog.shtml.
4. NCBI Bookshelf. (2000). The Origin and Evolution of Cells. Retrieved May 18, 2014, from http://www.ncbi.nlm.nih.gov/books/NBK9841/.
5. Hopkins, W.D., Lyn, H., Cantalupo, C. (2009). Volumetric and Lateralized Differences in Selected Brain Regions of Chimpanzees (Pan troglodytes) and Bonobos (Pan paniscus). The American Journal of Primatology. 71(12): 988-997. doi: 10.1002/ajp.20741 Retrieved May 18, 2014, from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2804891/
Gene homology diagram created by Maddy Ford