Genetic code Questions in English

(A) The genetic code for the amino acid tryptophan is $UGG$.
During the process of translation,the anticodon on the $t-RNA$ molecule is complementary to the codon on the $mRNA$ molecule.
Since the codon is $UGG$,the complementary anticodon will be $ACC$ (where $U$ pairs with $A$,and $G$ pairs with $C$).

(C) The correct answer is $C$.
The genetic code is said to be degenerate because some amino acids are coded by more than one codon.
In this case,both $UUU$ and $UUC$ code for the same amino acid,phenylalanine.
Note: The term 'non-ambiguous' means that one codon codes for only one amino acid,which is also a property of the genetic code,but the specific phenomenon of multiple codons coding for a single amino acid is defined as degeneracy.

(D) $AUG$ is a specific codon that serves two primary roles in protein synthesis.
First,it acts as the initiation codon,signaling the start of translation for the ribosome.
Second,it codes for the amino acid methionine $(Met)$.
Therefore,the correct option is $D$.

(A) $UAA$ is one of the three stop codons (nonsense codons) which do not code for any amino acid.
If the codon for the $25^{\text{th}}$ amino acid is mutated to $UAA$,the translation process will be terminated at that specific position because no $tRNA$ molecule can recognize the stop codon to bring the next amino acid.
Consequently,the ribosome will release the growing peptide chain after the $24^{\text{th}}$ amino acid.
Therefore,a polypeptide chain consisting of $24$ amino acids will be formed.

(C) The correct answer is $C$.
In the genetic code,the phenomenon where $61$ codons code for only $20$ different amino acids is known as degeneracy.
This occurs because some amino acids are specified by more than one codon.
This redundancy provides a protective mechanism against mutations,as a change in the third base of a codon (wobble position) often does not result in a change to the amino acid being incorporated.

(C) The statement "$UAA$ codon codes for lysine" is incorrect.
$UAA$ is a stop codon (also known as the ochre codon), which does not code for any amino acid and signals the termination of protein synthesis.
Lysine is actually coded by the codons $AAA$ and $AAG$.