The fire emoji next to a friend's name means that you and that special, special person in your life have snapped one another within 24 hours for at least two days in a row. You know, like your friendship is on fire? Or...
In adult humans, the most common hemoglobin type is a tetramer (which contains 4 subunit proteins) called hemoglobin A, consisting of two Î± and two Î² subunits non-covalently bound, each made of 141 and 146 amino acid residues, respectively. This is denoted as Î± 2 Î² 2.
There is more than one hemoglobin gene: in humans, hemoglobin A (the main form of hemoglobin present) is coded for by the genes, HBA1, HBA2, and HBB. The amino acid sequences of the globin proteins in hemoglobins usually differ between species. These differences grow with evolutionary distance between species.