Non-ABO, Non-Rh SystemsĪs it turns out, there are more than a dozen complete blood group systems other than the ABO system and the Rh system. In fact, most children who are O negative have parents who are positive, since the +- combination is so much more common than the - combination. Two parents who have O positive blood could easily have a child who is O negative. Most children who are O negative have parents who are positive, since the +- combination is so much more common than the - combination.In other words, their children could be either Rh positive or Rh negative. If both parents have Rh+ blood with the +- genes, they could have children who are ++, +-, or –.Only if your genetic type is - will you be Rh negative.If your genetic type is ++ or +-, your blood type will be Rh positive.In this system the positive are dominant over the negative.
These, however, are roughly grouped into positive and negative types. The Rh system is actually far more complex than the ABO system in that there are 35 different possibilities that one could inherit from each parent. These genes were first discovered in the rhesus monkey, hence the designation Rh. Conversely, if two parents both have type O blood, all their children will have type O blood.Īnother medically important blood type is described in the Rh system. A child with type O blood can have parents with type A, type B, or type O blood, but not type AB.A person whose genetic type is either AA or AO will have blood type A, those with genetic type BB or BO will have blood type B, and only those with genetic type OO will have blood type O.The A and B genes are co-dominant, and the O gene is recessive.Each person receives an A, a B, or an O gene from each parent.While there are rare exceptions, the following information on blood types applies to most people. Nevertheless, the genetics of human blood is far better understood than that of any other human tissue. The situation with human blood genetics is far more complex, since at each point there are multiple possible characteristics. Thus yellow was dominant over the recessive green gene. Those with a yellow and a green gene were also yellow only those with two green genes turned out to be to green. The peas with two yellow genes were yellow. Each pea has two seed-color genes, one from each parent. He worked with peas, which had easily distinguishable traits, such as green versus yellow seeds. Mendel’s first experiments, though simple, were quite profound. In order to express a recessive trait you must have two recessive genes. If you have one copy of a dominant gene you will express that trait, regardless of the other gene. Specifically, he recognized that some genes are dominant and some are recessive. The trait expressed, or visible, is a result of the interplay between these two genes. In his initial formulation, he described how sexual beings get two genes for each trait, one from each parent. Mendel’s work was unappreciated until 1900 - more than fifteen years after his death. The modern science of genetics had its start in 1866 when an Austrian monk named Gregor Mendel provided a simple yet powerful description of how traits are passed on from one generation to another. Genetics can be so confusing! I can easily see how after much research the issue about your parents would still appear murky.
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