Genetics as it applies to evolution, molecular biology, and medical aspects.
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A man whose blood group is Type A has two boys. The plasma of one of the boys agglutinates the red cells of his father, but the plasma from the other son does not. Which combination of the following statements.is correct?
I. The father must be heterozygous for the A blood type allele.
II. The mother of the son that agglutinates his father’s blood can be type AB.
III. The boy that agglutinates could have type O blood.
IV. The mother of the son that agglutinates must possess a type O allele.
V. The boy that doesn´t cause agglutination can be type AB.
A. I, II, V
B. I, III, V
C. I, IV, V
D. II, III, IV
E. II, IV, V
Here, v is true, AB type plasma doesnt have a or b agglutinin. So, D ELIMINATED.
III is wrong, O is universal donor. So its A or E. Can you help me from here?
if the father were homozygous, he could have only A or AB offspring, the plasma of neither would agglutinate his RBC. Ergo, the father is homozygous, I is true, A is the answer
The father is heterozygous, which makes him Ao, since he has A type. So I is true.
The non-reactive son could be AB or Ao. Neither reacts to A antigens. That makes V true.
The reactive son could be oo or Bo, which both react to A antigens. The mother could be oo, Bo, or AB. So II is true, but not IV. So is III.
So with I, II, III, and V true, we have a problem with the choices. What am I missing?
Sorry, I was such in a hurry I just chose between A and E. But yes, you are correct, type O blood has antibodies for both A and B antigens, so despite it being called "universal donor" the anti-A antibodies in his plasma would react to the A antigens on his son's RBCs. You aren't missing anything.
Are you sure this was not a deleted question?
BY the way, I wonder what i answered to this last year...
Hm, I saw it in a doc file I downloaded from a national biology olympiad website, (Argentinian, or portuguese, methinks).
The file carried the part B questions. If you want to check, it began with questions about ovulation, hormonal control of menstrual cycle and the likes. Dont you get the author solutions to all set problems after the IBO so you can check there?
This also came in Indian National Biology Olympiad 2008, slightly modified. The options were,
I father must be heterozygous Gr. A
II Children must have different mothers,
III 'agglutinaating' child could be of gr. O
IV mother of 'agglutinaating' child must be of gr. O
V 'non-agglutinaating' child could be gr. AB
A. I, II, V
B. I, III, V
C. II, III, IV
D. ONLY V
By the way, we learn in books that O is universal donor, and it can be given to any group. The valid plasma antibody argument you put forth makes me question, how can we tranfuse RBC without plasma?
The books are wrong? well, it all happens..........
you can of course separate RBCs from plasma. All you need to do is add an anticoagulant(citric acid or oxalic acid are used to bind Calcium ions) and then run it through a centrifuge. The heavier RBCs will sink to the bottom.
O is universal donor, because the RBCs have only the O antigen on its surface. But because it has antibodies against both A and B in the plasma, it is not recommended to give O blood to patients with other groups except if you don't have a choice(for the reasons stated above). Med School books here recommend that O blood can be given to another blood type only once and the transfusion should not exceed 500mL of blood.
the question is quite hard, i know...
but let me answer it.
If we analyze the question, it will show that one of the sons must be of O or B blood type, and this can only be achieved when the father is heterozygous.
that makes sure that case 1 is correct.
Eliminating answers without 1 would show that option 5 is correct.
Looking at the fact which is shown by answer 5, we'll deduct that the mother must either be heterozygous for B or of blood type AB.
the possible combinations for the children are:
1. The one who can coagulate his father's blood type:
- B heterozygous, or
2. The one who can't agglutinate his father's blood:
- A heterozygous, or
Yes, we concluded that I is true. The problem is I, II, III and V are true, and that is where the problem arises.
I agree with Mr. Mystery. There is some mistake with this problem. Maybe it was meant to say that mother must be AB? Then the answers would make sense.
For the part B - B. I, III, V is the answer.
To answer the question about blood transfusion:
Donor plasma does not carry sufficient amount of antibodies to recipient already depleted blood (plus their 'life' is quite short) to cause any problems. Recipient’s antibodies cause major problems if foreign antigens are introduced into the bloodstream on RBC.
Interesting question. I too wrote the Indian national Biology Olympiad 2009-2010. I have been selected among the top 30. Please can you guide me on how to prepare for the next stage which is a camp? you can email it to me.
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