Because their bodies tell them that they need more oxygen and so breathe faster, and try and get the oxygen their body requires and depends on.
The cause of mutations in gene expressions are the changes of gene instructions that causes your protein to malfunction. The effect of mutations are the genes not being able to function properly and send the wrong codes/info to your cells.
When charged amino acids within the interior of a protein attract, they form structure like salt bridges are are significant in determining the precise shape of the protein. This is because they attract one another strongly as opposed to the same charged molecules in a polar solvent like water.
