text: Two people with type A blood cannot produce a child with type B blood, but they can produce a child with type O blood.\n\nIn blood type, A and B are co-dominant, and O is recessive.  You inherit a gene from each of your parents, and they must both be O in order for you to have type O blood.  The same is not true with A and B.  Those types show themselves if you only inherit one gene for either one.\n\nIn your example, both parents have type A blood.  The possible gene combinations (or genotypes) to produce type A blood are AA and AO.  If two people who are both AO have a child, and both parents donate the O to their offspring, the offspring will have type O blood.\n\nWhen it comes to rh factor (the + and -), + is dominant, and - is recessive.  An A+ and A- couple can produce an O- child if the A+ parent carries the - gene.\n\nOne thing to note is that if we're talking about a real life example, be very concerned about the rh factor of the mother and the child.  If the mother has a different rh factor from the child, there could be serious problems with the pregnancy.\n\nI hope that was not overly complicated for you.