I think it's the first one. Performance isn't exactly "inconsequential", but it doesn't have to be purticularly good. In O(n) terms, it doesn't much matter because n is small(ish). It's more of a question of what the coefecient is.
(Which is one reason I think that O(n) is overused, but that's a question for another node.)TACCTGTTTGAGTGTAACAATCATTCGCTCGGTGTATCCATCTTTG ACACAATGAATCTTTGACTCGAACAATCGTTCGGTCGCTCCGACGC