Suppose we start with a single bacterial cell who's DNA is labeled with 15N. We allow the cell to grow and divide for 7 hours, which is ~21 generations in normal 14N containing media. This means there will be approximately 2 million cells in our final culture. Assume no cells die during this time, How many cells will contain 15N labeled DNA

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By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.

The answer is d i think