Interferon-alpha (IFN- $\alpha$ ) can be produced as a recombinant human protein to treat some types of cancer. The gene IFNA2 codes for IFN- $\alpha$.

One method of producing recombinant IFN- $\alpha$ uses genetically engineered Escherichia coli bacteria that contain recombinant plasmids. Each recombinant plasmid contains:
- the gene IFNA2
- three regulatory sequences of the lac operon (promoter, operator and lacl)
- a gene for antibiotic resistance, $A M P^{R}$.

Each of the sequences for the lacI gene and $A M P^{R}$ gene contains its own promoter. As a result, these genes are always expressed in E. coli bacteria that contain this recombinant plasmid.

Fig. 2.1 is a diagram of the recombinant plasmid. The promoter regions of the lacI gene and $A M P^{R}$ gene are not shown.

The enzyme glutamyl-tRNA reductase (GluTR) is present in many bacteria to make a product which is essential to their survival.

GluTR acts on the substrate glutamyl-tRNA, which is composed of the amino acid glutamic acid attached to a tRNA.

Fig. 3.1 shows the structure of glutamyl-tRNA and another compound called glutamycin.

Azotobacter vinelandii is a bacterium found in the soil that is able to fix atmospheric nitrogen. One feature of nitrogen-fixing bacteria is the ability to synthesise the enzyme nitrogenase, a molybdenum- and iron-containing, protein complex.

Sickle cell anaemia is a non-infectious chronic disease. If not treated, sickle cell anaemia can be painful and life-threatening.

Sickle cell anaemia is caused by a base substitution mutation in the gene coding for the $\beta$-globin polypeptide of haemoglobin. This leads to a change in the primary structure of the polypeptide, as valine is present instead of glutamine. This results in abnormal sickle-shaped red blood cells, which stick together in blood vessels.

Symptoms of sickle cell anaemia include painful attacks when red blood cells block capillaries in tissues and organs.

Spraying insecticide on the walls inside houses is the main method of controlling a species of Anopheles mosquito in rural India. A number of different insecticides have been used.

Malathion was the main insecticide used for many years. In 2005 the newer insecticide, deltamethrin, was used instead and the use of malathion was discontinued.

A laboratory study was carried out using mosquitoes collected from two sites in India. The percentage of mosquitoes killed by malathion and deltamethrin was estimated.

The results of the study are shown in Table 4.1

Maize is an important food crop that has been improved both by selective breeding and by genetic modification.

Food crops like wheat may be improved by selective breeding and genetic modification.