If you had a stem cell transplant, would your DNA change?

A fantastic question! It's not just stem cells you need to consider, but indeed any type of organ transplant or tissue donation. Another person, unless they are your identical twin, will have DNA different from your own. The reason lung transplants or bone marrow transplants actually work is because you are substituting dodgy tissue for healthy tissue. At the same time, you are replacing a gene that has gone wrong by putting in a healthy copy of the gene. That means the DNA in the tissue you've replaced will be different. The rest of your body won't change. If you do a bone marrow stem cell transplant for someone with leukaemia, the cells that you will have inside your bone marrow will come from your donor. Therefore, they will also be genetically identical to the donor. This means that a man who receives a bone marrow transplant from a lady will have bone marrow cells that have two X chromosomes. Sometimes people can even see a change in their blood group.