Assuming equal frequency for all 4 nucleotides (G, A, T, C), how many EcoRI recognition sites
(GAATTC) are possible in a bacterial artificial chromosome of 100,000 base pairs?
(A) 6 (B) 12 (C) 24 (D) 48
Answers
Answered by
3
the answer of this question is
(C) 24
(C) 24
Answered by
7
The correct answer is option (C) 24.
Explanation:
You know that EcoRI recognizes and cleaves GAATTC in a completely random DNA sequence. With 25%A's, 25%C's, 25%G's, 25%T's, we get GAATTC sequence once every 4096 base pairs.
Lets take 100,000 base pairs and mark every time a G occurs. We get 25,000 G's. Now, we need A in the second position, so sites containing GA is 25,000 * 0.25 = 6250. Now match another A. The sites will be 6250 * 0.25 = 1560. Similarly, we get 390 sites of GAAT, 100 sites of GAATT and 20 sites of GAATTC.
or, In short, you can use the concept of 4096 pairs, and get the answer as 100000/ 4096 = 25, which is approximately equal to 24.
Hence, option (C) is the answer.
Similar questions