この英文について質問があります。

At Oxford University, a more positive mentor encouraged him to try transplanting the nucleus of adult cells into frog eggs. The idea was to see if the genome — the hereditary information — stayed unchanged during development or underwent irreversible changes. In producing living tadpoles from the nucleus of adult frog cells, Dr. Gurdon showed that the genome of both egg and adult cells remained essentially unchanged.

But the possibility that animals, including humans, could be cloned did not seriously impinge on the public imagination until his work was reproduced in mammals with the generation of Dolly, the cloned sheep, in 1997. The following year saw generation of the first human embryonic stem cells, which are derived from the early human embryo. Such cells are called pluripotent because they can develop into any of the mature tissues of the body.

The two developments led to the concept of therapeutic cloning — take a patient’s skin cell, say, insert it into an unfertilized human egg so as to reprogram it back to pluripotent state, and then develop embryonic stem cells for conversion into the tissue or organ that the patient needed to have replaced. Since the new tissue would carry the patient’s own genome, there should be no problem of immune rejection.

　　　　　　　　　　　　　　（　http://investorstemcell.com/forum/stem-cell-news …より）

この文章の３段落目の最初のthe twoが指すものがわからないのですが、わかる方、ご回答をお願いします。　　　　　　　　　　　　　　　

No.1 ベストアンサー 回答者： SPS700 回答日時： 2012/12/25 16:46

　　　これは１段落目のオタマジャクシの場合と、第２段落目の哺乳類の場合との「二つ」です。

この回答へのお礼

ありがとうございます！

お礼日時：2012/12/25 19:57