Lecture 24 - Blood Groups and Pedigree Flashcards
Define antigen.
Antigen is any macromolecule that can induce an immune response.
In the ABO blood group, there are three alleles that determine the blood group. Explain the relationship between these alleles.
IA and IB are codominant. IA and IB are dominant to iO.
The gene locus for the ABO blood group is located on __________.
Chromosome 9
A father who has a O blood type just had his son’s blood type tested and discovered it to be O. He accused his wife of cheating as he knows his wife has an AB blood type. His wife denies this. You, a biology genius, know that there’s a high probability that she didn’t cheat. Explain and propose a test to prove your hypothesis.
There is a possibility that both parents are heterozygous for the Bombay, h allele and that their son is homozygous for the h allele (Bombay phenotype). A consequence of the Bombay phenotype is that the subject does not possess the H antigen, which is a precursor for both antigen A and B. Hence, even though the son possess the IA or IB allele, A or B antigen would not be present.
To test this hypothesis, test the son’s blood against another O blood type. If he has Bombay phenotype, it will react (coagulate) since the H antigen in the normal RBC will coagulate with the H antigen in the son.
Extra: Wife is AB. Regardless with which man she cheated on, there is no chance of having an O blood typed son, without accounting for the Bombay blood group, which is rare.
An O donor has no antigen in his RBC but have both antibodies A and B. An AB recipient has A and B antigen on his RBC and no antibodies. During transfusion, what do you expect to happen.
Nothing. No agglutination. Agglutination only occurs if the RBCs of the donor have the antigen for which the recipient has the antibody, not the other way around.
If you can answer this with explanation, good job.
A O- girl is involved in an accident and is brought to the hospital with massive haemorrhage. You, the blood bank supervisor, just found out that there is no more O- blood type reserves left. After reviewing her health history, you immediately gave her O+ blood. Justify your actions.
Even though the girl has no antigen D in her blood type, a Rh- individual has no naturally occurring D antibodies in blood. However, when exposed to the D antigen, the individual will start producing antibodies for the antigen, which becomes troublesome in the second exposure.
It is assumed that after reviewing the girl’s medical history, she has no previous transfusion or exposure with Rh+ blood with its D antigen. Hence, giving her O+ blood would not result in agglutination as it is her first exposure to the D antigen.
Describe features of a Y-linked pedigree.
- Only males expressed the phenotype
- A father possessing the phenotype will always inherit the feature to all of his sons.
Describe features of a autosomal recessive pedigree.
- Unaffected parents have affected child (skipping a generation)
- all children of two parents with the trait must have the trait
- approximately equal numbers of affected males and females
Exp. albinism, red hair colour
Describe features of an autosomal dominant pedigree.
- all affected individuals have at least one affected parent
- once the trait disappear from a pedigree branch, it does not reappear
- approximately equal numbers of affected males and females
exp. widow’s peak, achondroplasia
Describe features of an X-linked recessive pedigree.
- all sons of affected female are affected
- all children of two parents with the trait are affected
- none of the sons of an affected male and unaffected will be unaffected, unless mother is carrier (rare)
- more males than females will show the trait
exp. haemophilia, colour blindness
Describe features of an X-linked dominant pedigree.
- an affected male passes the trait to ALL his daughters
- every affected person has at least one parent with the trait
- if the trait disappears from a pedigree branch, it does not reappear
- more affected females than males
exp. vitamin D resistant rickets.
Describe features of a genetic heterogeneity pedigree.
- involves two families
- affected parents have no affected kids (not simple recessive or dominant)
