Q.(a) Write about incompatibility of Rh factor and how it can be prevented ? OR

(a) Rh incompatibility between an Rh-negative mother and Rh-positive foetus can cause haemolytic disease in a later pregnancy, prevented by anti-Rh immunoglobulin. (b) Species extinction has consequences at the individual-species, community/ecosystem, and global-biodiversity levels.

(a) The Rh blood-group system is a separate antigen system from ABO; individuals are Rh-positive if their RBCs carry the Rh (D) antigen, and Rh-negative if they lack it. Problems arise when an Rh-negative woman is pregnant with an Rh-positive foetus (having inherited the Rh-positive allele from an Rh-positive father). Normally, foetal and maternal blood do not mix during pregnancy, but a small amount of foetal blood can enter the mother's circulation at the time of delivery (or due to miscarriage, abortion, or certain prenatal procedures). Exposure to this 'foreign' Rh antigen stimulates the Rh-negative mother's immune system to produce anti-Rh antibodies, but since this response takes time to develop (as with any primary immune response), the first Rh-positive baby is usually born unaffected. However, if the same woman becomes pregnant again with another Rh-positive foetus, her already-primed immune system mounts a rapid secondary response, and her anti-Rh antibodies (being of the IgG class, which can cross the placenta) attack and destroy the foetal red blood cells, causing a serious condition called erythroblastosis foetalis (haemolytic disease of the newborn), which can result in severe anaemia, jaundice or foetal death. This is prevented by administering an injection of anti-Rh (Rho-D) immunoglobulin to the Rh-negative mother, usually within 72 hours of the first delivery (and after any other event risking foetal-maternal blood mixing); this passively administered antibody destroys any foetal Rh-positive cells that have entered the mother's blood before her own immune system can recognise them and mount an active response, so that she never actually produces her own anti-Rh antibodies or forms immune memory. …