(a)
$sequence1 = new Sequence::Nucleotide('gatcccgatttgcagtccaaa');
(b)
$sequence2 = new Sequence::Nucleotide($sequence1);
(c)
$sequence3 = $sequence1->new('gatcccgatttgcagtccaaa');
(d)
$sequence4 = new Sequence::Nucleotide('gatcccgatttgcagtccaaa','RNA');