Optically inactive amino acid is :-

Which of the following is not an essential amino acid?

$A$ codon has a sequence of $\underline{A}$,and specifies a particular $\underline{B}$ that is to be incorporated into a $\underline{C}$. What are $\underline{A}, \underline{B}, \underline{C}$?
$\underline{A} \quad \underline{B} \quad \underline{C}$

The number of chiral centres present in threonine is..........

Which of the following will not give a purple color with ninhydrin?

Which of the following amino acids has the lowest iso-electric point $(pI)$?