Question

Life as we know it depends on the genetic code: a set of codons, each made up of three bases in a DNA sequence and corresponding mRNA sequence, that specifies which of the 20 amino acids will be added to the protein during translation. Imagine that a prokaryote-like organism has been discovered in the polar ice on Mars. Interestingly, these Martian organisms use the same DNA → RNA → protein system as life on Earth, except that there are only 2 bases (A and T) in the Martian DNA, and there are only 17 amino acids found in Martian proteins. Based on this information, what is the minimum size of a codon for these hypothetical Martian life-forms? View Available Hint(s)

Answer 1

The right answer is 5.

To answer this question it is sufficient to take the same approach as the one that concluded that each amino acid is equivalent to 3 codons.

We have 17 amino acids, each of which must have at least one unique code (having two nucleotides A and T) .

it is enough to apply this time to count the number of possible codons to be generated according to the number of nucleotides:

nucleotide set ^ number of nucleotides = number of codons .

2 ^ 1 = 2 (<17)

2 ^ 2 = 4 (<17)

2 ^ 3 = 8 (<17)

2 ^ 4 = 16 (<17)

2 ^ 5 = 32 (> 17)

So, each amino acid has a codon of 5 nucleotides.