protected void addRandomNucleotide() {
		double dr = 4 * Math.random();
		Nucleotide nn = null;
		if (dr >= 0 && dr < 1)
			nn = Nucleotide.ADENINE;
		else if (dr >= 1 && dr < 2)
			nn = Nucleotide.GUANINE;
		else if (dr >= 2 && dr < 3)
			nn = Nucleotide.CYTOSINE;
		else if (dr >= 3 && dr < 4)
			nn = Nucleotide.THYMINE;
		addNucleotide(nn);
	}