GRE Reading Comprehension: Maggoosh-GRE阅读Maggoosh - D8N7SF6C225S5140N

The DNA molecule is composed of subunits called base pairs, which are two smaller subunits bonded together, forming part of a genetic message. In our bodies every individual cell has one billion base pairs. It is unlikely that all of these base pairs, making up what scientists call an entire genome, could be extracted from fossil remains. Even if they could, they would still need to be assembled into an ordered, structured genome. At present, isolating and organizing the DNA into an entire genome for a fossil animal is impossible. We cannot create carbon copies of organisms that are alive today, even if we have the entire genome in its correct order. Before cloning becomes possible, much must be learned about translating the information in the genome into a living, breathing organism.