First evidence for triplet genetic code was given by . . . . . . .

How many codons code for amino acids?

Which one of the following is a termination codon?

In the genetic code dictionary,how many codons are used to code for the $20$ amino acids?

$(i)$ The codon is read in mRNA in a contiguous fashion. There are no punctuations.
(ii) Some amino acids are coded by more than one codon.
(iii) $UUU$ would code for phenylalanine.
(iv) $GAA$ is a stop terminator codon.
Comparing the above statements (i-iv),select the correct option marked with $T$ (True) and $F$ (False) with respect to the salient features of the genetic code.

Hargobind Khorana received the Nobel Prize for his work on: