用取代率生成合成DNA序列

作为一个小优化,替换:

    $roll = int(rand 4) + 1;       # $roll is now an integer between 1 and 4

    if ($roll == 1) {$base = A;}
    elsif ($roll == 2) {$base = T;}
    elsif ($roll == 3) {$base = C;}
    elsif ($roll == 4) {$base = G;};

同

    $base = $dna[int(rand 4)];