There are almost 500 naturally occurring variants of hemoglobin. Most are the result of a single amino acid substitution in a globin polypeptide chain. Some variants produce clinical illness, though not all variants have deleterious effects. Identify the variant or variants that can be described by each of the three statements by placing the letter corresponding to the statement next to the variant. Statement B may describe more than one variant, and a variant may be described by more than one statement. At least one variant will not match any description. A. The Hb variant least likely to cause pathological symptoms. B. The variants most likely to show pI values different from that of HbA on an isoelectric focusing gel. C. The variant most likely to show a decrease in BPG binding and an increase in overall affinity for oxygen.

5. Hb Providence: substitutes an Asn for a Lys that normally decrease in BPG binding and an increase in overall affinity for oxygen B C projects into the central cavity of the tetramer

Answer:

1. HBd (sickle- Cell HH) substitutes a Val for Glu on the surface. (B)

2. Hg Memphis: Substitutrd one unchanged polar residue for another of similar size on the surface. (A)

3. Hb Milwaukee: subistitutes a Glu for a Val (B)

4. HB Philly Substitutes a Phe for a Tyr, disrupting hydrogen bonding. (B)

5. Hb Providence: substitutes an Asn for a Lys that normally decrease in BPG binding and an increase in overall affinity for oxygen B C projects into the central cavity of the tetramer (BC)

Explanation:

As you could see in the question above, there are more than 500 variants of Hemoglobin that occur naturally in the body. These variants can trigger the existence of syndromes and biological problems in the body, or not. However, it is important to note that all these variations are caused by simple changes and substitutions in the amino acid chain of hemoglobin that causes changes in the sequences of the nucleotides, interfering in the physicochemical activities of this protein. The severity of these changes depends on the extent of the mutation they caused and where the change took place.