(a)(i) Genes; are hereditary units/materials located on the chromosomes through which characters are transmitted from parents to offspring.
(ii) Gene mutation; is a spontaneous/sudden/unpredictable change in an individual gene which is persistent/ permanent/irreversible/heritable.
(b) The structures in plants and animals where mitosis and meiosis take place are listed below:
(i) Mitosis in plants: Root tip/stem apex; stem tip/ apex; cambium; meristems.
Mitosis in animals: Skin; damaged tissue; bone marrow; somatic cells/ wounded area of the body (e.g. skin).
(ii) Meiosis in plants: Ovaries; anthers.
Meiosis in animals: Ovaries; testes.
(c) Advantages of cross breeding two different breeds of cows are:
(i) Increased milk production.
(ii) Increased meat production/improved weight.
(iii) Resistance to diseases in the offspring.
(iv) Early maturity.
(v) Increased fecundity/reproductive capacity.
(d) Applications of genetics to medicine:
(i) Prevention of hereditary diseases.
(ii) Determination of the paternity of a child by use of DNN blood group.
(iii) Blood transfusion.
(iv) Production of insulin (to treat diabetes).