Genes are the primary units of inheritance in all organisms. A gene is a unit of heredity and corresponds to a region of DNA that influences the form or function of an organism in specific ways. All organisms, from bacteria to animals, share the same basic machinery that copies and translates DNA into proteins . Cells transcribe a DNA gene into an RNA version of the gene, and a ribosome then translates the RNA into a sequence of amino acids known as a protein. The translation code from RNA codon to amino acid is the same for most organisms. For example, a sequence of DNA that codes for insulin in humans also codes for insulin when inserted into other organisms, such as plants. 
When the cell is placed into a hypotonic solution, such as pure water, water moves into the cell and expands the plasma membrane against the cell wall. The cell wall is made of a rigid polysaccharide termed cellulose and does not expand with the enlarging membrane. In fact, the cell wall resists the expansion of the plasma membrane and creates a type of pressure within the cell termed turgor pressure . Such pressure is what makes your salad somewhat “crispy” when you consume it. What would happen to your salad if you soaked it in concentrated salt water for two hours before you consumed it (note: this is essentially what happens when plants wilt)? In the above figure (Figure ), the cell on the left is placed into a solution that is hypotonic with respect to the solution within the cell and the cell on the right is placed into a solution that is hypertonic with respect to the solution within the cell. Notice that when placed into a hypertonic solution, water exits the plant cell and the plant wilts. You can simulate this on your own if you wish: take a piece of lettuce and soak it in fresh water for 3 hours, take another piece of lettuce and soak it in concentrated salt water for 3 hours. Which one is crispy? Which one if flaccid? Can you explain these results?