Below is a list of the first 10 residues of the B helix in myoglobin from different organisms. Position 1 2 3 4 5 6 7 8 9 10
Human D I P G H G Q E V L
Chicken D I A G H G H E V L
Alligator K L P E H G H E V I
Turtle D L S A H G Q E V I
Tuna D Y T T M G G L V L
Carp D F E G T G G E V L
Based on this information, which positions (a) appear unable to tolerate substitutions, (b) can tolerate conservative substitution, and (c) are highly variable?