In: Biology
25. If proteins were composed of only 12 different kinds of amino acids, what would be the smallest
possible codon size in a genetic system with four different nucleotides?
A) 1
B) 2
C) 3
D) 4
E) 12
26. From the following list, which is the first event in translation in eukaryotes?
A) elongation of the polypeptide
B) base pairing of activated methionine-tRNA to AUG of the messenger
C) binding of the larger ribosomal subunit to smaller ribosome subunits
D) covalent bonding between the first two amino acids
E) Both B and D occur simultaneously.
If proteins were composed of only 12 different kinds of amino acids, the smallest possible codon size in a genetic system with four different nucleotides will be 2.
i.e, In normal we have about 20 different amino acids known naturally. So it can be coded only by triplet codon (since we have 4 bases viz, Adenine, Thymine, Cytosine, Guanine). That is 43= 64 (but 42=16 only).
Since the general formula is 4n. Here according to question (12 amino acids), the answer will be 2. (42= 16.)
In translation in eukaryotes the first event will be binding of small subunit the to mRNA, then binding of activated methionine- tRNA with to AUG. Then binding of larger subunit 60S. The next step is peptide bond formation with the incoming amino acid, followed by elongation.
According to the options the answer is B.