The genomic DNA of an organism has a base composition of 40% C-G base pairs and 60% A-T base pairs. Assuming a random sequence of bases, what is the expected frequency of the Tsp E1 restriction sites 5'-CCGG-3'?

The correct answer is (0.2)^4.

Explanation:

Based on the given information, the given genomic DNA is A-T rich, and the base pair composition is C-G = 40 % and A-T = 60%. Therefore, as per Chargaff's rule, Each C and G will possess 20%, and each A and T will possess 30%.  

Therefore, the probability of each base will be,  

C = 20/100 = 0.2

G = 20/100 = 0.2

A = 30/100 = 0.3

T = 30/100 = 0.3

Now the expected frequency of the Tsp E1 restriction sites 5'-CCGG-3' will be 0.2 * 0.2 * 0.2 * 0.2 = (0.2)^4.  

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