Why are there three rows, labeled a, b, and c, of possible amino acid sequences? What do the rows represent

1. Why are there three rows, labeled a, b, and c, of possible amino acid sequences?  What do the rows represent?  Why do we not know from the DNA sequence which row to use? 

2. Was the amino acid sequence always on the same row of possible amino acid sequences?  If so, why?  If not, how is it possible for the sequence to be on different rows? 

3. Was the amino acid sequence continuous once you found it?  If yes, why?  If not, how is it possible to be present in fragments in the gene? 

4. There are a few major reasons that a eukaryotic DNA gene sequence (from the +1 position to the terminator) is much longer than the resulting amino acid chain.  Describe two of them. 

5. Sickle-cell disease is the term for a group of genetic mutations in the hemoglobin heterotetramer protein that cause the shape of red blood cells to become sickle-shaped. Research sickle-cell disease and describe how the change in the shape of this protein ultimately causes a change in the shape of the entire cell in which the protein is produced. 

6. There are thousands of mutations that cause sickle-cell disease, but a very common one is a point mutation that changes an mRNA codon from GAG to GUG.  Name the amino acids produced from these two codons and describe why they are not functionally interchangeable (i.e., why replacing one for the other does not result in the same protein shape and therefore function). 

7. There are many environmental agents and factors that could cause proteins to denature.  In lab settings, the process of heating and the addition of a strong acid or base are common methods.  With reference to the amino acid properties in Figure 2, explain how the addition of a strong base (e.g. NaOH) could cause denaturation of a protein.