Permutations and combinations

Hey guys, I don’t get why the answer is A in this question. Why does the order matter?

It’s because 4 nucleotides can come at every single digit.

First letter: A, T , G, C possible = 4
Second letter: A, T , G, C possible = 4
Third letter: A, T , G, C possible = 4, an so forth.

Therefore all combos will be 4 * 4 * … * 4 = 4^7.

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