I have a question sir. According to Acts 17:26, He has made us from one blood. But nowadays why are there changes in our blood groups and genotypes?
Each individual has two sets of genes. Depending on the combination of those genes, we have different features, such as the color tone of our skin. See How did the different races come about?
There are three basic blood genes: A, B, and O. If a person has both genes, then he has type AB. If he has the genes for A and A or A and O, he has type A blood. If he has the genes for B and B or B and O, he has type B blood. If he has the genes for O and O, then he has type O blood. If Adam's blood type contained two of the traits (such as A and O) and Eve's blood type contained a different combination of the two traits (such as B and O), then the mixing of all the blood types would lead to all the various blood types we have today. See ABO Blood and Human Origins.
People who have different blood types are able to marry and have children, just as people of different skin colors are able to marry and have children. These traits do not make people a different race (or "kind" in biblical language) from each other.
Over time, God's creation has been wearing down because of mankind's sins from the beginning. Mutations (bad sequences of genetic code) have crept into the population. These have caused various genetic diseases but they do not cause people to cease being people.