Question

A certain bacterial mRNA is known to represent only one gene and to contain about 800 nucleotides. If you assume that the average amino acid residue contributes 110 Da to the peptide molecular weight, the largest polypeptide that this mRNA could encode would have which of the following approximate molecular weights (in Da)?

		800
		5,000
		30,000
		80,000

Answer 1

mRNA codes for the protein, codons are three nucleotides which code for an amino acid, one codon is stop codon which does not code for any amino acid.

so maximum number of codons in 800 nucleotides long mRNA is 800/3=266.7

maximum number of codons in 800 nucleotides long mRNA is 266.

number of codons which codes for amino acids= number of codons-1=266-1=265

mass of one amino acid= 110 Da

so mass of 265 amino acids long protein is 110265=29150

the approximate molecular weight of the protein is c) 30000