Question

For an imaginary Martian species with three nucleotides (X, Y and Z), how many 3-letter codons are possible?

• A. 64
• B. 27
• C. 9
• D. 4

Hint:

To find the total number of codons, use the formula: (number of nucleotides)\(^3\). For 3 nucleotides, it’s \(3^3 = 27\).

Answer 1

The Correct Option is B

Step 1: Understand the definition of a codon.
A codon is a sequence of three nucleotides that together form a unit of genetic code in a DNA or RNA molecule.

Step 2: Determine the number of nucleotide options.
In this imaginary species, there are only three types of nucleotides: X, Y, and Z.

Step 3: Calculate all possible 3-letter codons.
Each position in the codon (first, second, and third) can be filled by any of the 3 nucleotides. So, the total number of codons is:

3 × 3 × 3 = 27

Step 4: Eliminate other options.
64 codons result from 4 nucleotides (as in Earth life):

43 = 64

9 codons would come from 2-letter sequences:

32 = 9

4 is irrelevant in this context.