What is one molecular technique that has made reviving extinct species more of a possibility? Explain how the technology works.What are (at least) two barriers to reviving extinct species?

Read How to Clone a Mammoth by Beth Shapiro and watch on YouTube “How to Clone a Mammoth: The Science of De-Extinction – with Beth Shapiro”. In a three-page, double-spaced essay, address the following questions:

1) What are (at least) two barriers to reviving extinct species?
2) What is one molecular technique that has made reviving extinct species more of a possibility? Explain how the technology works.
3)Finally, address the ethical considerations of de-extinction. Do you think reviving extinct species is ethical? What is your biggest concern?

https://www.youtube.com/watch?v=xO043PSBnKU