Clover leaf secondary structure of $tRNA$ has a loop for

The aminoacylation of $tRNA$ is known as:

At which end does the amino acid attach to $t-RNA$?

In a polypeptide chain consisting of $125$ amino acids,if the $25^{th}$ amino acid codon mutates to $UAA$,what will happen?

How many amino acids are present in the polypeptide which is synthesised from the translation of the following $m-RNA$ sequence?
$5'-UUUUCUAUGCUGGUGGCUUGAUUUUCCCCU-3'$

Which of the following acts as a catalyst in a bacterial cell?