4) A recessive genetic condition can prevent some people from expressing the carbohydrate core that is typical for the O blood type. As a result of this condition, two parents with A, B, or AB blood types who are carriers of this recessive condition could have a child with neither A, B, nor AB blood; such a child would be unable to receive blood from anyone who did not have the same condition. Briefly explain why these children would be unable to make the A and/or B antigens given their condition and why they would not be able to receive blood from A, B, AB, or O blood types.