Consider the structure of double-stranded DNA. When DNA is placed into distilled water, it denatures; however, by adding NaCl, the DNA renatures. Why?
What will be an ideal response?
The negatively charged phosphates repel each other on the two sides of the helix. In distilled water, these charges are not neutralized (by positively charged ions), and the hydrogen bonds, which hold the double helix together, are broken. In the presence of positive ions, such charges are neutralized.
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The endocrine gland that controls homeostasis in terms of blood glucose levels is the
A. parathyroid gland. B. adrenal gland. C. pineal gland. D. pancreas. E. testis.
Which cells are not normally involved in the functioning of the immune system in humans?
A) white blood cells B) red blood cells C) lymphocytes D) B cells
At what level of organization does life begin?
A. Reproductive organs B. Cell C. Molecule (water) D. Molecule (DNA) E. Population
What accounts for rigor mortis?
What will be an ideal response?