For the Human Genome Project, cloning of large segments of our genome was first made possible by the development of yeast artificial chromosomes, which are capable of propagating in the yeast Saccharomyces cerevisiae just like any of the organism's 16 natural chromosomes. In addition to the cloned human DNA, these artificial vectors were made to contain three elements that are necessary for them to function as a chromosome. What are these elements? Write down the names of the elements in alphabetical order, and separate them with commas, e.g. gene, histone, nucleosome.