7 Turn over 4 The photograph shows a blood smear from a healthy person, as seen using a light microscope. K J Source: © biophoto associates/science photo library (a) (i) Which row of the table identifies the cells labelled J and K? (1) Cell J Cell K A eosinophil lymphocyte B lymphocyte neutrophil C monocyte eosinophil D neutrophil monocyte (ii) Which is the approximate ratio of erythrocytes to leucocytes in this blood smear? (1) A 1 : 50 B 3 : 50 C 50 : 1 D 50 : 3 8 (b) Chronic myelogenous leukaemia (CML) is a blood disorder. The photograph shows a blood smear from a person with CML, as seen using a light microscope. Explain why a blood smear can be used to diagnose CML. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... 9 Turn over (c) The diagram shows some stages in the production of blood cells from bone marrow stem cells. Bone marrow stem cell Common lymphoid progenitor cell Common myeloid progenitor cell Megakaryocyte Myeloblast Mast cell Erythroblast Basophil Neutrophil Eosinophil Monocyte Small lymphocyte Natural killer cell B lymphocyte T lymphocyte Explain how a bone marrow stem cell differentiates into either a common myeloid progenitor cell or a common lymphoid progenitor cell. (4) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (Total for Question 4 = 8 marks)