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Hemoglobin is a multimeric protein made of two types of protein chains and its structure is often listed as ${ \alpha }_{ 2 }{ \beta }_{ 2 }$. There are over 300 variants of hemoglobin that all result from a mutation in the gene that encodes either the ${ \alpha }$ or ${ \beta }$ protein subunit. Sickle cell anemia is caused by a mutation in the gene that encodes the ${ \beta }$ subunit; more specifically, a glutamate is changed to a valine. This change does not change the overall shape of the subunit greatly, but the hydrophobic valine seeks out other hydrophobic amino acids on nearby subunits. The mutation that leads to sickle cell anemia thus disrupts:

I. Primary (${ 1 }^{ ° }$) structure.
II. Tertiary (${ 3 }^{ ° }$) structure.
III. Quaternary (${ 4 }^{ ° }$) structure.

Which of the following BEST describes the effect of the mutation that causes sickle cell anemia on hemoglobin?

A

I and II.

B

I and III.

C

II and III.

D

I, II, and III.

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