Your DNA blood type is determined by the type of antigens in your red blood cells. There are both A and B antigens. A person with A antigens has what is called Type A blood. A person with B antigens is said to have Type B blood. A person who has both the A and the B antigens in their blood has Type AB blood. Someone without either A or B antigens is said to have Type O blood.
The implications for the type of blood you have are great as far as DNA is concerned. Your DNA blood type determines eligibility for organ transplants and blood transfusions. You can only receive transfusions and transplants from someone with compatible and matching DNA. If the wrong type of blood is used when performing such operations, the body will reject the operation with grave consequences.
DNA blood types can also be used to help prove genealogy, ancestry, and in some cases, paternity. This often helps others assemble their family tree and can also determine Native American ancestry. It can help people determine their roots of where they came from as well as maternal and paternal lineage. DNA blood types has been able to unlock many secrets and has forever changed the lives of many.
Finally, DNA has recently been used to help prove innocence or guilt in criminal cases. Many prisoners have been exonerated after being convicted of a crime and serving in prison for several years. Others have had their guilt confirmed; helping families of victims find ultimate justice in knowing the truth.