DNA supercoiling means under or over winding of the DNA strand and basically is to become more condensed and more organized. Supercoiling is very important as it compacts the genetic code and as if that was not enough supercoiling also regulates and oversees the access the the genetic code.
A head injury happens due to trauma to the brain or skull and classified as close or sometimes penetrating. It may occur right away or develop slowly. An example is contusion which is the answer on this scenario. This is called mild traumatic injury caused by a blow on the head yet none of the tissue of the brain is torn.