This was the least popular question in this part and most candidates avoided it, those candidates who attempted it scored low marks. Many candidates could not define gene, and gene mutation. In stating the structures in plants where meiosis takes place some candidates were saying flower, seed, instead of ovaries and anthers. Candidates also gave. broad answers for advantages a farmer may derive from crossbreeding e.g. to obtain offspring with 'hybrid vigour. Expected answers include;
Definitions
Genes - are hereditary units/materials, located on the chromosomes; through which characters are transmitted from parents to offspring.
Gene mutation - is a spontaneous/sudden/unpredictable change in an individual gene, which is persistent/permanent/irreversible/heritable.
Mitosis in plants
Root tip/apex; stem tip/apex; cambium; meristems.
Mitosis in animals
Skin; damaged tissue; bone marrow/somatic cells/wounded area of the body (e.g. skin).
Meiosis in plants Ovaries; anthers.
In Animals Ovaries; testes.
Advantages of cross breeding
- Increased milk production;
- Increased meat production/improved weight;
- Resistance to diseases in the offspring; early maturity;
- Increased fecundity/reproductive capacity.
Applications of genetics to medicine
- Prevention of hereditary diseases;
- Determination of the paternity of a child by use of DNA/blood group;
- Blood transfusion;
- Production of insulin (to treat diabetes).
