1.1 WHAT IS GENETIC ENGINEERING?
Genetic engineering or genetic modification is the alteration or modification of an organism’s genome using modern DNA technology (Biotechnology). It usually involves the introduction of foreign DNA or synthetic genes into the organism; the new resulting organism is often referred to as transgenic and or genetically modified (GM). New DNA is obtained either by isolating or copying the genetic material of interest or by artificially synthesizing the DNA (Muntaha et al., 2016).
The headways that have been made in Genetic Engineering have its foundation in the discovery of DNA molecule in 1953 (Watson-Cricks-Wilkins-Franklin model WCWF Model) (Muntaha et al., 2016).
The first genetically modified organisms (GMOs) were bacteria in 1973 and the first genetically modified (GM) animals were mice in 1974.
The term ‘Genetic Engineering’ was first coined by Jack Williamson in his science fiction novel ‘Dragon’s Island’, published in 1951, but genetic engineering as the direct manipulation of DNA by humans outside breeding and mutations did not start until the 1970s.
1.2 DEFINITION OF SOME KEYWORDS
BIOTECHNOLOGY: American Chemical Society defines biotechnology as the application of biological organisms, systems, or processes by various industries to learning about the sciences of life and the improvement of the value of materials and organisms such as pharmaceuticals, crops and livestock. Basically, biotechnology is the use of or the manipulation of living cells for research to understand science of life and to produce new and improved products.
Medical biotechnology specifically involves the use of living cells to research and produce diagnostic and treatment products that help to treat and prevent human diseases.
RECOMBINANT DNA: This is a DNA molecule that has been produced from the combination of multiple genetic materials to create sequences that would ordinarily not be found in the genome.
GENOME: An organism’s genome is it’s compete DNA set, including all its genes. It contains all of the organism’s information.
DNA: Deoxyribonucleic acid is the hereditary material in humans and almost every other living organism because it carries the genetic instructions of growth, reproduction, development and general functioning of all living organisms and many viruses. The DNA has a Double Helix structure.
MEDICINE: This is simply the science of healing. It involves diagnosis, treatment and prevention of diseases.
1.3 APPLICATION OF GENETIC ENGINEERING
Genetic engineering has numerous applications in numerous fields including research, agriculture, industrial biotechnology and medicine.
With the development of recombinant deoxyribonucleic acid (DNA) technology, the metabolic potentials of living organisms are being discovered and put to use in a variety of new ways. Today, genetically modified microorganisms (GMMs) are applied extensively in human health, agriculture, and bioremediation and in industries such as food, paper, and textiles. Genetic engineering offers the advantages over traditional methods of increasing molecular diversity and improving chemical selectivity. In addition, genetic engineering offers an abundant supply of desired products, cheaper product production prices, and safe handling of otherwise dangerous agents (Lei et al., 2004).
Genetic engineering in agriculture for example has lead to the production of transgenic plants, plants that had foreign traits incorporated into them that made them have better yield and enhanced nutritive value of crop has gathered much interest to combat malnutrition in developing countries. A very interesting trait that has been genetically engineered into crops is the resistance to pesticides or insecticides (Singh et al., 2014).
1.4 APPLICATION OF GE IN MEDICINE
In medicine, the advent of genetic engineering and biotechnology has greatly helped in diagnosis, cure or treatment, and prevention of several diseases. Medical Biotechnology has four specific applications, which are:
1. Gene therapy
2. Pharmacology
3. Stem cells
4. Tissue engineering
Genetic Engineering has made some remarkable achievements in medical science dealing with diseases and reducing the chances of it being passed to the next generation (Sandel, 2014).
Chapter 2
GENE THERAPY
Gene therapy a GE process is used to treat genetic diseases like Alzheimer’s, Cystic Fibrosis or cardiovascular diseases that can be passed from one generation to the next. The advancements being made in biotechnology and GE have brought gene therapy in the limelight. Gene therapy which is developed with the establishment of recombinant DNA and gene cloning methods is considered an innovative therapeutic technology. It is basically associated with alteration of human hereditary material used to deal with biomedical abnormalities (Hongxin and Yuguan, 2015). The working principle of gene therapy is the correction of the faulty gene that is causing the genetic disease. For instance, there has been success achieved by researchers in altering the lymphocytes of patients having cancer, eye, immune system or blood diseases genetically (Aubourg, 2016). Gene therapy’s importance in cancer treatment is increasing as new technologies are developed. Gene therapy can be carried out by either of the following methods:
• Inserting a normal gene into a nonspecific location
• Swapping abnormal gene for normal gene
• Repairing abnormal gene
• Turning a gene on or off
CHAPTER 3
PHARMACOLOGY:
Drugs are also produced by genetic engineering; these drugs are called Biopharmaceuticals. Generally speaking, any drug produced by using microorganisms or process of genetic engineering falls under the category of Biopharmaceuticals (Muntaha et al., 2016). The production of genetically engineered human insulin was one of the pioneer breakthroughs of biotechnology in the pharmaceutical industries. The first time insulin produced through recombinant DNA technology entered clinical trials was in 1980. Genetic engineering has been used in medicine to produce or synthesize the following biopharmaceuticals:
• Antibiotics,
• Hormones (e.g. Insulin, Human growth hormones),
• Enzymes,
• Vaccines,
• Follistim (for treating infertility),
• Human albumin,
• Monoclonal antibodies,
• Antihemophilic factors,
• Drugs from plants.
3.1 GENETIC ENGINEERING IN INSULIN PRODUCTION
3.1.1 WHAT IS INSULIN?
Insulin is an important hormone that is secreted by the pancreas. Insulin regulates the metabolism of carbohydrates, proteins, fats; but specifically it controls the blood sugar level, it regulates the blood sugar preventing it from getting too high (hyperglycaemia) or too low (hypoglycaemia).
After eating, blood sugar level rise, beta cells in the pancreas receive a signal and they release insulin into the blood stream, the insulin then bind to signal cells to absorb sugar from the bloodstream. If there’s more sugar in the body than it needs, the storage of the excess sugar is controlled by insulin.
The secretion of insulin by the beta cells of the pancreas is in response to various ‘stimuli’ like glucose, arginine, and sulphonylureas though physiologically glucose is the major determinant. Various neural, endocrine and pharmacological agents can also exert stimulatory effect. Glucose is taken up by beta cells through GLUT-2 receptors. Glucose in the beta cell is oxidized by glucokinase, which acts as a glucose sensor. Glucose concentration below 90 mg/dl does not cause any insulin release (Shashank et al., 2007).
3.1.2 Insulin as a treatment for diabetes:
People with type 1 or type 2 diabetes need insulin injections to allow their body to process glucose and avoid complications from hyperglycaemia (high sugar level).
In type 1 diabetes patients, the pancreas cannot make insulin because the beta cells are either damaged or completely destroyed while type 2 diabetes patients are resistant to insulin. Therefore insulin injections have to be administered so that their sugar levels will be controlled and complications from hyperglycaemia will not occur.
Subsequently, there are various analogues of insulin classified based on their mode and duration of action (Gualandi-Signorini et al., 2001), they include:
Rapid-acting insulin
Short-acting insulin
Intermediate-acting insulin
Long-acting insulin
3.1.3 SYNTHESIS OF HUMAN INSULIN
Insulin extracted from the pancreas tissue of animals was used for therapy from 1922 until 1974, when semi-synthetic human insulin became available in limited quantity by modification of animal insulin (Ruttenberg, 1972). This method is based on the identification of the structure of human insulin gotten from autopsy and the subsequent engineering of animal insulin’s structure into human insulin.
3.1.3.1 Humulin:
Humulin is synthetic human insulin produced by using genetic engineering using the recombinant DNA technology in the laboratory. Genetically engineered insulin can carry out all the functions the natural human insulin carries out. In 1978, scientists synthesized human insulin from Escherichia coli bacteria using recombinant DNA technology, by preparing two DNA sequences for A and B chains of human insulin and introduced them into the plasmid of Escherichia coli. This led to production of human insulin chain.
Insulin can also be produced from yeast like (Saccharomyces cerevisiae, Pichia pastoris) by recombinant DNA technology.
The simple principle is the introduction of human insulin or proinsulin into the organism i.e. Escherichia coli, Saccharomyces cerevisiae after which the organism mass produce insulin when it undergoes cell division and growth. The process for recombinant human insulin was initiated by Genentech in 1978 (Miller, and Baxter, 1980).
Production of recombinant human insulin starts with the insertion of a gene encoding the precursor protein pre-pro-insulin into a DNA vector that is transferred into a host i.e. Escherichia coli or yeast (Frank et al., 1983). During the product synthesis, the culture and fermentation conditions are controlled optimally to optimise yields (Frank et al., 1981). A fusion protein obtained by fermentation is converted to bioactive human insulin by post-translational processing.
The final step in the manufacturing process is the multi-step purification of human insulin until the necessary high extent of purification is obtained. This is followed by crystallisation of the final product and pharmaceutical manufacture of the different insulin products (Sandow et al., 2015).