biological evidence - blood serology

serology

is the scientific study of blood serum and other bodily fluids, it refers to the diagnostic identification of antibodies in the serum

blood components

red blood cells, white blood cells, platelets and plasma (55% blood 90% water) liquid fraction, when blood allowed clot liquid fraction is called serum (fibrin proteins forms a mesh and entraps cells

blood grouping

before dna typing blood grouping or typing was used in conjunction with other serotyping methods to partially individualise a blood sample on non-dna genetic markers

pre dna systems

reffered to as classical or conventional genetic markers, doesnt target dna specifically, AB antigen has genetical code

pcr

polymerase chain reaction

red blood cell antigens

rbc carry oxugen around body also have structure on cell surface called antigens, antigen are protein made from the dna inherited by parents, blood antigens grouped into systems >30, A-B-O system and rhesus systems are important

ABO

sugar antigen

ABO blood typing

1901 by karl landsteiner, first used in 1916 in italy, type A has A antigens on cell surface, type B has B antigens on cell surface, type AB have both A and B antigens, type O have neither, A- anti B antibodies, B- anti A antibodies, O- both anti A and anti B, AB- neither A nor B

agglutination

the visible clumping of particles that occurs when antibodies bind to antigens on their surface, presence or apsence of agglutination when ABs added to blood determines blood group

how agglutination occurs

serum containing anti-B is added to rbcs that have B antigen then antibody binds to antigen on cell surface

cross linked cells

each AB can attach to different rbcs so the network becomes cross linked

AB-

universal respicates

O

universal

rhesus system

56 antigens, 5 most relevent - E, e, C, c and D, the D determines if its + or -, haemolytic disease when mother has rhesus D and baby doesnt can poison baby or opposite way around