This web page was produced as an assignment for Genetics 564, an undergraduate course at UW-Madison
What is Homology?
Homology is defined as shared ancestry of structures and genes that are seen between species (1). Homology arrises from common ancestors shared between species. Homologies can be quantified on both a molecular and phenotypic level. Pictured left are phenotypic homologies between the forearms of several different species. The similarity between the forearms of a human and a bat may seem surprising until we look deeper into the molecular basis of these similarities. By using an online tool called BLAST we can compare the DNA, mRNA, or proteins between different species. BLAST quantifies homology between species with percent identity which reflects the percent of the sequences that match between two species (2). Here DNA sequences between different organisms were compared. DNA is made up of nucleotides which code for different amino acids to result in proteins. However, some nucleotides are in non-coding regions of DNA, meaning that they are not translated to proteins, explaining why the DNA and protein homology are not exactly the same
Figure 1: Forearm homologies between
different organisms
different organisms
In order to gain a greater understanding of how conserved COL3A1 is among different species, reciprocal BLASTS were ran between the humans against the species below and percent identities were obtained.
Homo Sapiens (Humans) COL3A1
Accession: NM_000090
Accession: NM_000090
Pan Troglodytes (Chimpanzee) COL31A
Accession: XM_001163809.3 Percent Identity: 99% E-Value: 0.0 Macaca Mulatta (Rhesus Macaque) COL31A Accession: NM_001266039.1 Percent Identity: 98% Evalue: 0.0 Rattus Norvegicus (Rat) Col31a Accession: NM_032085.1 Percent Identity: 87% E-Value: 0.0 |
Mus Musculus (Mouse) Col31a
Accession: NM_009930.2 Percent Identity: 86% E-Value: 0.0 Gallus Gallus (Chicken) COL31A Accession: NM_205380.2 Percent Identity: 74% E-Value: 0.0 Xenopus Tropicalis (Western Clawed Frog) Col3a1 Accession: NM_001011005 Percent Identity: 79% E-Value: 3e-30 |
Analysis
COL3A1 is very well conserved between species indicating its importance to survival. A percent identity of 74% between chickens and humans, two anatomically distant species reinforces the importance of collagen in the development of many different structures. Because of its conservation, COL3A1 can be studied in many different model organisms. However, due to the biological function of collagen, COL3A1 is not observed in many traditional model organism species including fruit flies and zebrafish, leaving fewer choices for study.
References:
1) "Homologies." Understanding Eolution. University of California Museum of Paleontology, Web. 25 Mar. 2015. <http://evolution.berkeley.edu/evolibrary/article/lines_04>
2) Wheeler, David. BLAST QuickStart. U.S. National Library of Medicine, n.d. Web. 25 Mar. 2015. <http://www.ncbi.nlm.nih.gov/books/NBK1734/.>
3)"Basic Local Alignment Search Tool." BLAST Web. 23 Mar. 2015. <http://blast.ncbi.nlm.nih.gov/Blast.cgi>.
1) "Homologies." Understanding Eolution. University of California Museum of Paleontology, Web. 25 Mar. 2015. <http://evolution.berkeley.edu/evolibrary/article/lines_04>
2) Wheeler, David. BLAST QuickStart. U.S. National Library of Medicine, n.d. Web. 25 Mar. 2015. <http://www.ncbi.nlm.nih.gov/books/NBK1734/.>
3)"Basic Local Alignment Search Tool." BLAST Web. 23 Mar. 2015. <http://blast.ncbi.nlm.nih.gov/Blast.cgi>.