Adult human haemoglobin usually contains two $\alpha$ chains together with two $\beta$ chains. Around $5\%$ of humans possess one amino acid in the $\beta$ chain that has been altered. This alteration changes the structure and stability of haemoglobin. Which levels of protein structure might be affected in the haemoglobin of the humans with the altered amino acid?
- Aprimary only
- Bprimary and quaternary only
- Csecondary, tertiary and quaternary only
- Dprimary, secondary, tertiary and quaternary