Editing Hemoglobin (section)

==Evolution of vertebrate hemoglobin==
Scientists agree that the event that separated myoglobin from hemoglobin occurred after [[lamprey]]s diverged from [[jawed vertebrate]]s.<ref name="Goodman-1975">{{cite journal |title=Darwinian evolution in the genealogy of haemoglobin |journal=Nature |date=1975-02-20 |pages=603–08 |volume=253 |issue=5493 |last1=Goodman |first1=Morris |last2=Moore |first2=G. William |last3=Matsuda |first3=Genji  |bibcode=1975Natur.253..603G |pmid=1089897 |doi=10.1038/253603a0 |s2cid=2979887}}</ref> This separation of myoglobin and hemoglobin allowed for the different functions of the two molecules to arise and develop: myoglobin has more to do with oxygen storage while hemoglobin is tasked with oxygen transport.<ref name="Storz-2013">{{cite journal |title=Gene duplication, genome duplication, and the functional diversification of vertebrate globins |journal=Molecular Phylogenetics and Evolution |date=2013-02-01 |issn=1095-9513 |pages=469–78 |volume=66 |issue=2 |last1=Storz |first1=Jay F. |last2=Opazo |first2=Juan C. |last3=Hoffmann |first3=Federico G.  |pmid=22846683 |doi=10.1016/j.ympev.2012.07.013 |pmc=4306229|bibcode=2013MolPE..66..469S }}</ref> The α- and β-like globin genes encode the individual subunits of the protein.<ref name="Hardison-2012">{{cite journal |title=Evolution of hemoglobin and its genes |journal=Cold Spring Harbor Perspectives in Medicine |date=2012-12-01 |issn=2157-1422 |pages=a011627 |volume=2 |issue=12 |last=Hardison |first=Ross C.  |pmid=23209182 |doi=10.1101/cshperspect.a011627 |pmc=3543078}}</ref> The predecessors of these genes arose through another duplication event also after the gnathosome common ancestor derived from jawless fish, approximately 450–500&nbsp;million years ago.<ref name="Goodman-1975"/> Ancestral reconstruction studies suggest that the preduplication ancestor of the α and β genes was a dimer made up of identical globin subunits, which then evolved to assemble into a tetrameric architecture after the duplication.<ref name="Pillai-2020">{{cite journal |last1=Pillai |first1=Arvind S. |last2=Chandler |first2=Shane A. |last3=Liu |first3=Yang |last4=Signore |first4=Anthony V. |last5=Cortez-Romero |first5=Carlos R. |last6=Benesch |first6=Justin L. P. |last7=Laganowsky |first7=Arthur |last8=Storz |first8=Jay F. |last9=Hochberg |first9=Georg K. A. |last10=Thornton |first10=Joseph W. |date=May 2020 |title=Origin of complexity in haemoglobin evolution |journal=Nature |language=en |volume=581 |issue=7809 |pages=480–85 |bibcode=2020Natur.581..480P |issn=1476-4687 |pmid=32461643 |doi=10.1038/s41586-020-2292-y |pmc=8259614 |s2cid=218761566}}</ref> The development of α and β genes created the potential for hemoglobin to be composed of multiple distinct subunits, a physical composition central to hemoglobin's ability to transport oxygen. Having multiple subunits contributes to hemoglobin's ability to bind oxygen cooperatively as well as be regulated allosterically.<ref name="Storz-2013"/><ref name="Pillai-2020"/> Subsequently, the α gene also underwent a duplication event to form the ''HBA1'' and ''HBA2'' genes.<ref>{{cite journal |vauthors=Zimmer EA, Martin SL, Beverley SM, Kan YW, Wilson AC |title=Rapid duplication and loss of genes coding for the alpha chains of hemoglobin |journal=Proceedings of the National Academy of Sciences of the United States of America |date=1980-04-01 |issn=0027-8424 |volume=77 |issue=4 |pages=2158–62 |bibcode=1980PNAS...77.2158Z |pmid=6929543 |doi=10.1073/pnas.77.4.2158 |doi-access=free |pmc=348671}}</ref> These further duplications and divergences have created a diverse range of α- and β-like globin genes that are regulated so that certain forms occur at different stages of development.<ref name="Storz-2013"/>

Most ice fish of the family [[Channichthyidae]] have lost their hemoglobin genes as an adaptation to cold water.<ref name="Sidell-2006"/>