Chapter 8 - Technology used to treat disease Flashcards
what is DNA
Found in the nucleus, mitochondria and cytosol. Consists of 2 strands of nucleotides (deoxyribose sugar, phosphate group and a nitrogenous base). Twisted in a double helix, bases attached by hydrogen bonds. The order of the 4 bases (A, T, C, G) is the genetic info that determines the structure and function of the cell
Artificial selection
Humans select desired traits and choose parents based on these traits. Slow and inefficient as genes are passed on by chance and have to wait for next generation to mature before knowing outcome. Also called selective breeding
Genetic engineering
Procedures used to produce recombinant DNA. involving introducing DNA into a cell from a different type of organism. Also known as recombinant DNA technology
Recombinant DNA
synthetic DNA made by inserting genes from one source into a DNA molecule from a different source
GMO
Genetically Modified Organism, produced by genetic engineering
Transgenic organism
Organism that has had DNA from another species introduced into it artificially. All transgenic organisms are GMO’s, but not all GMO’s are transgenic.
example of a transgenic organism
Golden rice. Transgenic organism produced by introducing a gene from maize and a bacterium found in soil into rice. Allows rice to produce beta carotene which the human body can use to synthesise vitamin A
who invented the recombinant DNA technique and when
Stanley Norman Cohen and Herbert Boyer in 1973
cohens and boyers technique
Isolate and amplify genes or DNA segments and insert them into bacterial cell, creating a transgenic bacterium. The introduced genes become part of the transgenic organism’s DNA and is passed to the next generation
two steps for genetic engineering to be possible
- gene for desired trait must be identified and then isolated
- DNA receiving the gene must be ‘opened’, then added to the recipient and joins its DNA
Bacteriophage
A virus that infects bacteria
Recognition site
Specific sequence of nucleotide at which a restriction enzyme cuts a strand of DNA. 4-8 base pairs long
Restriction enzyme
enzyme that cuts strands of DNA at a specific sequence of nucleotides (recognition site). Examples of endonucleases
Endonucleases
enzyme that breaks a nucleic acid within the strand by separating two nucleotides
What are the two types of cuts and ends that restriction enzymes can produce
- Straight cut (clean break across two strands of DNA) producing blunt ends (both strands terminate in a base pair, no overhang, not specific)
- Staggered cut (fragments of DNA with unpaired nucleotides) producing sticky ends (overhanging complementary bases, is specific, cut at different positions on strand)
Palindromic
Sequence that reads the same forward and backwards. recognition sites are palindromic
two factors that contribute to the type of cut
- Recognise a certain base sequence
- Cut at a certain point
DNA ligase
An enzyme capable of combining two small components of single stranded DNA into one single structure
Ligation
The process of joining short strands of DNA during replication
how does DNA ligase work
By joining the phosphate group at the end of one strand to the sugar molecule at the end of another strand
Vector
A bacterial plasmid or other agent used to transfer genetic material from one cell to another
what are the steps to producing an organism with recombinant DNA
- Identifying the desired gene
- Using restriction enzyme to cut the DNA on either side of the gene
- Using the same restriction enzyme to cut the DNA of the vector
- Adding the desired gene to the vector
- Using DNA ligase to join the two sections of DNA
Plasmid
In bacterial cell, small circular strands of DNA distinct from main bacterial genome. Replicates independently of the chromosomal DNA
Examples of the use of recombinant DNA technology
Enabled the manufacture of large quantities of pure protein for many medical products including insulin, GH, factor 8 and FSH
What are vaccines that are currently being investigated focused on
Using recombinant bacterium E.coli or cells from mammals, insects or yeast to produce protein antigens These can be introduced into the body to elicit an immune response
Recombinant vaccines
Vaccines produced using recombinant DNA. vaccine for hepatitis B and HPV is produced using recombinant technology
DNA vaccine
A vaccine that stimulates an immune response by introducing antigen DNA, which causes the host cells to produce the antigen
What are the two disadvantages of DNA vaccines
- Expensive: genes for the desired antigens must be located, cloned and expressed efficiently in a new vector.
- Conservative: those in vaccine research must be conservative as vaccines are used on large numbers of healthy people and safety is paramount. If a conventional vaccine is known to be safe there is little incentive to develop a new vaccine using genetic engineering
examples of disorders that lead to the body being unable to produce certain hormones
Type 1 and 2 diabetes mellitus, hyperthyroidism and hypothyroidism
Diabetes
group of diseases which result in an abnormally high level of glucose in the blood and excretion if glucose in the urine
Hyperglycemia
an abnormally high blood glucose level. frequently found in people with diabetes
what is not possible for someone with diabetes
A balance between insulin and glucagon keeps blood glucose at correct level for normal body functioning
what are the two types of diabetes and their alternative names
- Type one diabetes mellitus (insulin dependent)
- Type two diabetes mellitus (adult onset or insulin independent)
What is type one diabetes (NP)
Form of diabetes that develops rapidly, usually before 20. Caused by a decline in insulin producing cells of the pancreas. Treated by injections of insulin. Beta cells produce insulin, therefore person with type one diabetes does not produce insulin but cells still respond to it in normal way
what causes type one diabetes
Not caused by lifestyle, is genetic. A fault in the immune system causes the destruction of beta cells of the islets of langerhans in the pancreas
what is type two diabetes (NR)
Usually develops in people 45+. They are able to produce insulin but cells do not respond to it. If left untreated can increase risk of heart disease, stroke, kidney disease, eye problems, nerve damage and skin and foot problems. Management includes careful diet, physical activity, healthy weight, monitoring blood glucose
What causes type two diabetes
Lifestyle disease, factors of increasing risk include:
- Lack of physical activity
- Overweight/obese
- High fat, sugar and salt, low fibre diet
- High blood pressure + cholesterol
- Smoking
Is preventable, no cure, suffering reduced by healthy lifestyle.
how is diabetes treated
Injections of insulin obtained from pancreas of cows and pigs, making supplies of insulin expensive and limited. In 1980s genetically engineered human insulin began to be produced. The gene for human insulin was inserted into DNA of E.Coli. The bacteria was cultured, and the transgene allowed bacterial cells to produce the protein of human insulin which was then extracted and used to treat people
Thyroid disorders
The thyroid gland is located in the neck and secretes thyroxine (T4) and and triiodothyronine (T3). It is important in a long-term homeostasis of body temperature by gradual change in metabolic rate that occurs from summer to winter. And excess of or a deficiency in thyroxine can cause disorders. This may be due to a problem in thyroid or imbalance in TSH
What is hyperthyroidism
Overactivity of the thyroid gland resulting in abnormally high levels of thyroid hormones in the blood. Most common type of hyperthyroidism is known as Graves’ disease. Not inherited but is genetic predisposition for condition
what are the symptoms of hyperthyroidism
Because cells are overstimulated and metabolic rate is increased, the symptoms are: rapid heartbeat, weight loss, increased appetite, fatigue, sweating, anxiety, protruding eyeballs (exophthalmia)
how is hyperthyroidism treated
Treated with drugs that block thyroids use of iodine (During the production of T3 and T4 iodine is absorbed from the bloodstream, concentrated in cells in the thyroid and then incorporated into the molecules to produce the hormones), drink containing radioactive iodine (The radioactive iodine molecules are taken up by the thyroid cells which are then killed by the radioactivity. Radioactive iodine is eventually excreted in urine), surgery to remove some or all of thyroid (therefore less hormones produced)
What is hypothyroidism
More common, occurs through problems with the thyroid, pituitary gland or hypothalamus. Is the underactivity of the thyroid gland resulting in low levels of thyroid hormones in the blood
what are the symptoms of hypothyroidism
Symptoms arise due to decrease in metabolism and may include slow heart rate, unexplained weight gain, fatigue, lack of energy, intolerance to cold, face swelling, goitre
what are the causes of hypothyroidism
Although a severe iodine deficiency can cause hypothyroidism, most common is an attack on the thyroid by the patients immune system (Hashimoto’s disease). Another cause is surgery for cancer of the thyroid that removes part or all of the gland
how is hypothyroidism treated
If the cause is lack of iodine, treated with extra iodine in the diet. For treatment of other causes, tablet containing thyroid hormone are prescribed. No cure, tablets are taken for life. Dose carefully monitored as to little can lead to hypothyroidism and too much can lead to hyperthyroidism. Tablets used to be made with Dried and powdered thyroid glands of pigs but today most made synthetically
Goitre
Swelling of the neck caused by an enlargement of the thyroid in an effort to increase hormone production
Gene therapy
The treatment of disease by replacing, manipulating or supplementing non-functional jeans in cells and tissues. Research concentrating on single gene disorders such as cystic fibrosis, Huntington’s, muscular dystrophy, sickle cell anaemia and type one diabetes. Unlike most medicines which treat the symptoms of a disease, Gene therapy has the potential to correct the underlying cause
The human genome project
A project with the aim of mapping the base pairs and identifying the genes in human DNA
What are the four areas of possibility for gene therapy
- Replacing a mutated gene with a healthy copy
- Fixing or inactivating mutated genes
- Inserting a new gene that will fight the disease
- Making the immune system recognise diseased cells
What is the concept of gene therapy
That a vector can be used to deliver desired DNA into a cell. This DNA can be incorporated into the cells nucleus and undergo transcription to produce the desired protein
Gene therapy in type one diabetes
Looks at methods of making it possible for body to produce insulin again by reprogramming other cells to produce insulin. Achieved by introducing the gene for insulin into a vector. Vector is then used to infect the desired cells, such as alpha cells in the islets of langerhans. These cells incorporate the new DNA into their nucleus and are able to use protein synthesis to produce insulin
Cystic fibrosis
Mainly affects the lungs and pancreas but sometimes the liver and reproductive organs. Characterised by thick sticky mucus secreted by the mucous glands. In the lungs, this mucus may clog the tiny air passages and trap bacteria, making a person with CF susceptible to infection. Repeated infections and continual blockage of airways may cause irreversible lung damage and decreased life expectancy. Pancreas also affected, preventing secretion of enzymes required for digestion leading to frequent problems with nutrition. CF results when an individual inherits the recessive allele for the condition from each parent. Corrected faulty genes in cultured cells by adding normal copies of genes
Cell replacement therapy
The replacement of damaged cells with healthy ones. Any disorder involving the loss of, or injury to, normal cells is a potential candidate for stem cell replacement therapy. Cell replacement therapy for the nervous system has generated the most interest due to the debilitating nature and widespread occurrence of neurodegenerative disorders such as Parkinsons and Alzheimers
Tissue engineering
The rebuilding of damaged tissue by the use of biology, medicine and engineering. The primary objective of tissue engineering is to restore healthy tissues or organs for patients and thus eliminate the need for tissue organ transplants. Requires an abundant supply of disease free cells of specific types. These cells need to be induced to grow on a scaffold of natural or synthetic material to produce a three-dimensional tissue. Scaffolds serve as a template for tissue growth and need to have high pore sizes that enable the cells to grow while at the same time allowing the diffusion of nutrients throughout the whole structure. They also need to be biodegradable. Once the scaffold has been devised, suitable stem cells need to be cultured. The cells are seated onto the scaffold which then enables further growth and proliferation. This cell coverage scaffold is then implanted into the patients at the site when you tissue is required. As the new cell continues to grow and divide the material making up the scaffold begins to degrade or in some cases be absorbed. Such tissue engineering techniques are being used to develop a wide range of tissues including bone, skin, Cartlilage and adipose tissue
