GENETICS OF BLOOD Flashcards
what are blood group antigens?
carbohydrate structures present on red cell membrane glycoproteins and glycolipids.
what is the ABO gene?
a gene that determines the blood group of an individual by modifying the oligosaccharides on cell surface glycoproteins.
what antigen does blood group O have on their surfaces?
H antigen (basic with nothing added)
What enzyme does the ABO gene code for in order to produce the A antigen?
N-acetylgalactosaminyltransferase
What enzyme does the ABO gene code for to produce the B antigen?
Galactosyltransferase (forms galactose and B antigens)
what is isoagglutinogen?
one of the antigens naturally occurring on the surface of red blood cells that is attacked by an isoagglutinin in blood plasma of a different group, so causing agglutination.
why is blood group inheritance not the same as Mendelian inheritance?
because A and B are codominant
if 2 people both have the same phenotype (blood group A), do they have the same genotype?
no because there are 3 possible alleles IA IB and I, so you could get blood group A from IA i or IA IA.
what would happen if you gave blood group B to an individual with blood type A?
agglutination because blood group A contains anti-B antibodies which would bind to blood group B, clump together.
What blood types can you give to an individual with blood type B?
B or O
why is AB blood referred to as universal recipient?
because it can receive blood from any type due to having no antibodies in their serum. (they do have A and B antigens on their surface however)
Why can blood groups AB only give blood to other AB groups?
as they contain both A and B antigens on their surface
why is blood group O referred to as the universal donor?
because you can give the blood to any blood group due to no antigens on their surface
who can blood group O receive blood from?
just O individuals as they have both A and B antibodies in their serum that would cause agglutination otherwise.
what does it mean if an individual is rhesus positive? what is rhesus negative?
it means that the D protein is found on the surface of the red blood cells. rhesus negative means these antigens are not present.
what’s more common, RHD+ or RHD-?
RHD+ (85% of the population)
how many copies of the gene do you need to have to be RHD+?
you can be homozygous for RHD or hemizygous (maybe due to a deletion)
how many blood groups do we have? what are they?
8; A+ A- B+ B- AB+ AB- O+ O-
what specifically is the universal donor and recipient blood group?
donor- O-
recipient- AB+
how does rhesus disease come about?
what is this effect called?
if a RhD- women becomes impregnated by a RhD+ man and this forms a RhD+ baby. if the mother is exposed to the foetal blood then she can make antibodies against the D proteins so if she went on to have a second child who was RhD+ then the antibodies could cross the placenta and attack the foetal blood.
sensitisation
how can rhesus disease be prevented?
by being screened and having an injection of a medication called anti-D immunoglobulin which will bind and neutralise any RhD+ cells to prevent the development of maternal antibodies.
how can we minimise transfusion reactions?
how do we do this?
doing cross matching checks to see if the blood is compatible
we take a blood sample and add in antiA antibody to see if we get agglutination. we try this with Anti-B and Anti-D antibodies too.
what are haemoglobinopathies?
inherited blood disorder in which an individual has an abnormal form of haemoglobin (variant) or decreased production of haemoglobin (thalassaemia)
what is sickle cell anaemia caused by?
a mutation in the beta globin chain where glutamic acid is replaced by valine to form HbS.
