What is homology?
Learning Vocabulary
Homology is the study in which a structure is conserved across related species and adapted in form and function for each organism. By using a comparative approach and assuming the principle of parsimony, one can parse out the common ancestor's structure. Figure 1 shows a simple example of bone morphology. The same can be applied to microscopic level structures, like proteins and genes. Gene Homology |
Figure 1. Homology of forearm structures across mammalian species.
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Homologous genes, or homologs, are derived from a common nucleotide sequence in a common ancestor. These genes might have small sequence changes that alter amino acid structure when transcribed, but overall one would likely expect higher percent identity in more related species and less in more distant. If a gene maintains the same function within two organisms, the gene is orthologous, or an ortholog.
Homologous Gene ReferencesWhen using the BLAST tool to search for homologs to the MEFV gene, BLAST was only able to return results for Pan, Macaca, Canis and Bos on "High similar sequences (megablast)" [1]. By reducing the similarity profile to "Somewhat similar sequences (blastn)", I was able to recover reliable homologs for Rattus, Mus and and Danio.
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Homo sapiens - Mediterranean fever (MEFV), transcript variant 1, mRNA
Accession Number: NM_000243.2 FASTA Homo sapiens - Mediterranean fever (MEFV), transcript variant 1, mRNA Accession Number: NM_001198536.1 E-value: 0.0 Max ID: 83% FASTA Pan troglodytes - Mediterranean fever, transcript variant 2 (MEFV), mRNA Accession Number: XM_523280.3 E-value: 0.0 Max ID: 98% FASTA Macaca mulatta - Mediterranean fever (MEFV), mRNA Accession Number: XM_001092338.2 E-value: 0.0 Max ID: 93% FASTA Canis lupus familiaris - Mediterranean fever (MEFV), mRNA Accession Number: XM_547161.3 E-value: 0.0 Max ID: 81% FASTA |
Bos taurus - Mediterranean fever (MEFV), mRNA
Accession Number: XM_002697878.2 E-value: 2e-150 Max ID: 80% FASTA Rattus norvegicus - Mediterranean fever (Mefv), mRNA Accession Number: NM_031634.1 E-value: 5e-108 Max ID: 78% FASTA Mus musculus - Mediterranean fever (Mefv), transcript variant 1, mRNA Accession Number: NM_001161790.1 E-value: 5e-114 Max ID: 71% FASTA Danio rerio - bloodthirsty-related gene family, member 12 (btr12), mRNA Accession Number: NM_001076619.1 E-value: 8e-07 Max ID: 79% FASTA |