Discussion on: Daily Challenge #175 - Complementary DNA

private static string DNA_strand(string dna)
{
    var sb = new StringBuilder();
    var bytes = Encoding.ASCII.GetBytes(dna);
    foreach (var b in bytes)
    {
        if ((b & 0b0000_0010) == 0)
        {
            sb.Append((char) (b ^ 0b0001_0101));
        }
        else
        {
            sb.Append((char) (b ^ 0b0000_0100));
        }
    }

    return sb.ToString();
}