Explain why individuals with type O blood can donate to any other blood type, and why individuals with type AB
blood can accept blood of any blood type. What will be an ideal response?
ANSWER: ABO blood types are determined by a gene I (I for isoagglutinin) encoding an enzyme that
alters a cell-surface protein. This gene has three alleles, IA, IB, and iO—often written as A, B,
and i. The dominant A and B alleles each produce a slightly different version of the enzyme,
and the recessive i allele produces no enzyme. People with type A blood have A antigens on
their red blood cells and do not produce antibodies against this cell-surface marker. However,
people with type A blood do make antibodies against the antigen encoded by the B allele.
Those with type B blood carry the B antigen on their red cells and make antibodies against the A antigen. If you have type AB blood, both A and B antigens are present on your red
blood cells and no antibodies against A and B are made. If you have type O blood, you have
neither antigen but do make antibodies against both the A antigen and the B antigen.
Because AB individuals carry no antibodies against A or B, they can receive a
transfusion of blood of any type. Type O individuals have neither antigen and can donate
blood to anyone, even though their plasma contains antibodies against A and B; after
transfusion, the concentration of these antibodies is too low to cause problems
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The relationship between a pathogen and its host is best described as ____
Fill in the blank(s) with the appropriate word(s).
The binomial system of nomenclature assigns each organism a scientific name consisting of ________.
A. kingdom and species B. kingdom and genus C. genus and species D. species and strain
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