How many proteins of average size could be encoded in a virus with a dna genome having 12000 bp assuming no overlap of genes?

Given: Virus genome of size 12000 bp, no overlap of genes.

To find: The number of protein molecules that can be synthesised from genome.

Solution:

The average size of protein in virus is 400 aa.

1 codon = 3 bp = 1 aa  (Codon codes for 1 amino acid, and a codon consists of 3 nucleotides)

A 400 aa sized protein will need 400 codons = 3 x 400 = 1200 bp

Hence the total number of proteins that can be made is,

Total size of genome in bp/Size of 1 protein in bp = 12000/1200 = 10

The answer is 10 proteins of average length 400 aa.