Question

A restriction endonuclease has a recognition site of 3 bases. Assuming random arrangement of nucleotides, the probability that this endonuclease will cut a piece of DNA is __________ (rounded off to three decimal places).

Answer 1

Correct Answer: 0.015

To determine the probability that a restriction endonuclease with a 3-base recognition site will cut a piece of DNA, we must consider the randomness in nucleotide arrangement. In DNA, there are 4 possible nucleotides: adenine (A), thymine (T), cytosine (C), and guanine (G). For each position in the recognition site, any of the 4 nucleotides can occur. Hence, the total number of unique sequences that could potentially match the recognition site is 4³, as there are 3 bases in the recognition site.

Calculate: 4³ = 4 × 4 × 4 = 64.

The probability that a specific sequence of 3 bases will appear by chance is 1 out of these 64 possibilities.

Thus, the probability (P) is computed as:

P = 1/64.

Converting this to a decimal gives:

P = 0.015625.

Rounded to three decimal places, P = 0.015.