JWs teach that Adam was a physically perfect, free moral agent. Adam's sin did not cause him to lose physical perfection, rather God took it away. This would imply that God altered/corrupted Adam's DNA. In so doing, God chose to condemn all of us, because we inherited Adam's corrupted DNA.
JWs teach that the "Tree of Life" was only symbolic, and had no supernatural life-granting properties.
“[Jehovah] then had to act as Judge, supporting and applying his own statement of the consequences.— Watchtower 09 2014
God had told Adam: “In the day you eat from [the tree of the knowledge of good and bad] you will certainly die.” Adam may well have understood this “day” to be a 24-hour day. After violating God’s command, he could have expected Jehovah to act before the sun set....
Then [Jehovah] pronounced sentence on the wrongdoers. Were he to execute them then and there, his purpose regarding Adam and Eve and their offspring would come to nothing. Although he confirmed the death penalty and the effects of sin began immediately, he allowed Adam and Eve to produce children who could benefit from other provisions that He would make. Thus, from God’s standpoint, Adam and Eve died on the day they sinned, and they actually died within one “day” of 1,000 years.”
“GOD’S human sons were not meant to die. (Romans 8:20, 21) In fact, when Jehovah first spoke of death to Adam, it was mentioned, not as the outcome that man should normally expect, but as the punishment for disobedience to God.”— Awake! 10/07 2007
“the Creator himself decreed the death sentence for the first human pair, implementing that sentence in a way that man does not fully understand...”— Insight, Volume II pg. 247
“The first reference to death in the Scriptures occurs at Genesis 2:16, 17 in God’s command to the first man concerning the eating from the tree of the knowledge of good and bad, violation of which command would result in death. However, death among animals as a natural process was evidently already in effect, since they are passed over completely in the Biblical presentation of the introduction of death into the human family. The gravity of God’s warning about the death penalty for disobedience would therefore be understandable to his human son, Adam. Adam’s disobedience to his Creator brought death to him. Thereafter, Adam’s sin and its consequence, death, spread to all men.”“Adam and Eve also experienced a physical change. God condemned them to death, just as he had said he would. They became imperfect, and this led to the corrupting of the whole human race—their offspring.”— Watchtower 06/15 1984
“When Adam was created, God placed in the garden of Eden “the tree of life.” This tree evidently had no intrinsic life-giving qualities in its fruit, but it represented God’s guarantee of life “to time indefinite” to the one whom God would allow to eat of its fruit.”— Insight, Volume II, pg. 245
