Changes in the dna are called mutations. They can occur spontaneously. Mutations can only be passed down in gametes--sperm and egg cells. with Darwins theory at mind a mutation needs to pass the test of natural selection to remain in the gene pool. So purposly making mutation or altercations may end in diseases/illnesses or in some cases death because they body can not take it.....hope this helps if it doesnt im sorry!
Membrane proteins can function as enzymes to speed up chemical reactions, act as receptors for specific molecules, or transport materials across the cell membrane. Carbohydrates, or sugars, are sometimes found attached to proteins or lipids on the outside of a cell membrane.
The process by which the oceanic crust<span> is pulled </span>under<span> the </span>continental crust<span> is called </span>subduction<span> and the zone at which this occurs at the plate boundaries is called the </span>subduction<span> zone.</span>
