Flashcards in Chapter 23 - Biotechnology Deck (57):
A genome is the complete set of genetic information of an organism.
- For humans this is the complete sequence of the nucleotides that make up the 20 000 - 25 000 genes in our chromosomes.
What is a hereditary disease?
A hereditary disease is caused by defective genetic information being transmitted from parents to their children.
When do mutations occur?
At times, a particular gene may, quite suddenly, change from its original structure and produce a totally different characteristic.
-Mutations, because they involve a change in the genetic material, can then be passed on to future generations.
Describe the structure of DNA molecules.
-All DNA molecules consist of two strands of alternating sugars (deoxyribose) and phosphates with pairs of nitrogen bases forming cross-links between the sugar molecules in the two strands.
-The molecule is twisted into a spiral known as a double helix.
-The order in which the nitrogen bases occur in the DNA molecule is the genetic information that determines the structure of the cell and the way it functions.
What is DNA sequencing?
It is the determination of the precise order of nucleotides in a sample of DNA.
Further elaborate on the structure of the DNA.
DNA is synthesised from four nucleotides, more correctly called deoxynucleotide triphosphates, as each nucleotide consists of three phosphate groups joined to the sugar deoxyribose.
2. Each nucleotide has a different base - adenine, cytosine, guanine or thymine.
Explain the process of DNA sequencing.
1. In building a sequence, each new nucleotide is bonded to the hydroxyl group (OH) of the previous nucleotide.
2. In Sanger's method of determining a DNA sequence, synthetic nucleotides that lack this OH group are added to the growing strand.
3. The synthetic nucleotides stops the elongation of the sequence because there is no OH group for the next nucleotide to attach to.
4. This technique then allows the strands to be compared.
What will comparing DNA sequences allow a person to see?
-Changed alleles can be detected and will show whether an individual has a particular disease.
-Point mutations, as well as small insertions or deletions are readily identified by DNA sequencing.
What are examples of disease that use DNA sequencing to detect?
1. Spastic Paraplegia - inherited disorder that causes progressive limb weakness and stiffness, often resulting in paralysis.
2. Sickle-Cell Anaemia, Cystic Fibrosis & some forms of cancer - with the knowledge that they have inherited faulty allele, people are able to seek effective treatment, and possible prevent the disease or, at least, decrease its effects.
3. Paternity/ Maternity test.
What is Electrophoresis?
It is a technique which involves the DNA pieces being placed on a bed of semi-solid gel and an electric current was passed through electrodes located at either end.
How can an individual's DNA fingerprint (DNA profile) be identified?
The DNA which is negatively charged, move faster than the larger ones, resulting in a pattern of bands that looks similar to the barcodes on produces sold in supermarkets.
What are DNA fingerprints useful for?
1. Tracing ancestry and in forensic science.
2. Identification of hereditary disease, such as Cystic Fibrosis or Huntington's Disease. (even for newborns)
If an individual has a particular gene does that mean they will have the disease?
-A recently discovered allele has been sown to increase an individual's risk of colon cancer.
-DNA profiling enables this allele to be identified and a person with it can then have regular medical examinations, even though colon cancer may never develop.
What is the polymerase chain reaction (PCR)?
It is a technique widely used in molecular biology.
Segments of DNA are artificially multiplied through a series of repeated cycles of duplication using an enzyme called DNA polymerase.
What is a Primer?
-To initiate duplication a primer is required.
-The primer is a segment of DNA, complementary to the targeted sequence of DNA, which initiates replication by the DNA polymerase.
List the steps of Polymerase chain reaction .
1. By using DNA polymerase, the original molecule of DNA is replicated doubling the number of DNA molecules.
2. Each molecule is then replicated in a second sequence of replication, resulting in four times the number of original molecule.
3. A third sequence of replication occurs, again doubling the number of molecules of DNA, and so on.
What is the benefit of PCR?
-By using PCR, an original DNA template can be amplified over many sequences to generate millions of copies of the original DNA molecule.
-Such compounding amplification of the original molecule has resulted in the process being called a chain reaction.
Give an example and explain what is 'heat-stable DNA polymerase'.
- On such enzyme, taken from a heat-loving bacterium called Thermus aquatics, is called Taq polymerase.
-This does not break down when heated and it has allowed the procedure to be simplified and automated, permitting the PCR sample to be alternately heated and cooled.
-Such steps are necessary as heat is required to separate the strands of DNA but cool conditions are essential for the synthesis of the DNA by the enzyme.
What disease can be detected using this method ?
1. Sickle cell anaemia
2. Phenylketonuria (PKU)
3. Cystic Fibrosis
4. Viral disease
5. Forensic Science - used to amplify the DNA from a single drop of blood or semen, or a strand of hair, thus allowing sequencing to take place and a DNA fingerprint to be produced.
What is a Genetic Probe?
AKA gene probe is a fragment of DNA (or RNA) labelled with radioactive isotopes or a fluorescent marker that is used to detect the presence of a specific sequence of bases in another DNA (or RNA) molecule.
What is Genetic Probe used for ?
Genetic probes are used extensively to detect the presence of the allele responsible for hereditary disease such as cystic fibrosis, Huntington's disease, Duchenne muscular dystrophy and thalassaemia.
How is a human chromosome and targeted band located by a genetic probe?
-The Human Genome Project has made the location of all the genes in the human genome available to scientists, so that they are now able to use that data in their research.
-Genes suspected, or known, to be involved in a particular disease can be targeted.
1. Therefore, if part of the base sequence of a gene under investigation is known, a genetic probe can be made to locate its presence.
2. The probe is a single strand of matching DNA labelled with a radioactive or fluorescent marker.
3. The DNA being examined is denatured to split the double strands into single strands.
4. The genetic probe is then mixed with this material, seeks out the complementary base sequence and binds to it.
5. In this way the probe identifies exactly where the target gene is located.
Which hereditary diseases have been detected by the genetic probe?
1. Duchenne Muscular Dystrophy
What is Recombinant DNA technology (aka genetic engineering)?
It involves the introduction into cells of DNA that is foreign to the organism, or that has been modified in some way.
What is genetic engineering used for?
1. It can be used to take genes from one organism and place them into the chromosomes of another.
- This has huge potential for replacing faulty genes with healthy ones.
2. It could be used for the benefit of patients suffering from cystic fibrosis, rheumatoid arthritis and certain cancers.
3. The same technology is another way of identifying mutations and determining whether a person is affected by, or is a carrier for, hereditary diseases.
4. Another technique was to isolate and amplify genes or DNA segments and insert them into a bacterial cell creating a transgenic bacterium.
What are Transgenic Organisms?
-Transgenic Organisms are those whose genome has been altered by the transfer of a gene or genes form another organism.
-The introduced genes become part of the transgenic organism's DNA and can be passed on from one generation to the next.
What are bacteriophages/ phages?
Viruses that infect bacterial cells.
What is the key breakthrough that lead to recombinant DNA technology?
The discovery that certain enzymes in bacteria are able to restrict the duplication of infecting viruses, by cutting up the viral DNA.
-Scientists discovered that such an enzyme always cuts the DNA at a point where there is a specific sequence of bases.
What is another major breakthrough in being able to modify genes?
The discovery of an enzyme that was able to join, or recombine, separate pieces of DNA.
Define Restriction enzyme.
Enzymes that cut strands of DNA at specific sequences of nucleotides.
An enzyme that is capable of combining two small components of single-strand DNA into one single structure.
-Some version of DNA ligase is used by every living cell to "glue" together short strands of DNA during replication, a process called Ligation.
Or bacteriophage; a virus that infects bacteria.
Small circular strands of DNA distinct from the main bacterial genome; they are composed of only a few genes and are able to replicate independently within cells.
Define Blunt Ends.
The ends produced by a straight cut of a sequence of nucleotide bases.
Define Staggered Cut.
Produced when a restriction enzyme creates fragments of DNA with unpaired nucleotides that overhang at the break in the strands; called sticky ends.
Define Straight Cut.
Produced when a restriction enzyme makes a clean break across the two strands of DNA so that the ends terminate in a base pair; called blunt ends.
Define Sticky ends.
The overhanging ends produced by a staggered cut of a sequence of nucleotide bases; can be called cohesive ends.
Bacterial plasmids, viral phages or other such agent used to transfer genetic material from on cell to another.
When can single-stranded breaks in phage DNA be repaired?
-Researches found that this can only happen in the presence of ligase.
-They demonstrated that ligase was able to form a bond between a particular end of the last nucleotide on one DNA fragment with a complementary end of the last nucleotide on an adjacent fragment.
-This discovery enabled scientists to attempt their own recombination experiments.
-Such experiments involved not just recombining the DNA of a single organism but recombining DNA from different organisms, including different species.
Explain the steps in producing an organisms with recombinant DNA.
MEMORISE DIAGRAM ON PAGE 362.
List examples of the use of Recombinant DNA technology.
2. Human Growth Hormone
3. Factor VIII
How has the use of Recombinant DNA tech assisted in patients suffering Diabetes?
1. The human gene that has the code for insulin production was introduced into bacterial cells.
2. These bacteria became insulin factories and are now cultured in vats where they produce insulin that can be used to treat diabetes.
3. The insulin produced by the bacteria is identical to human insulin because the human gene was engineered into the bacteria.
What is Human Growth Hormone (hGH) ?
They are synthesised and secreted by cells in the anterior pituitary.
What happens when there is a deficiency in hGH?
A deficiency of hGH results in growth retardation or dwarfism, and can result from either inheritable or acquired disease.
-Children with severely retarded growth can be treated with injections of growth hormon.
How has the use of Recombinant DNA tech assisted in hGH?
1. With the advent of recombinant DNA tech, hGH is now made by genetically engineered E. coil bacteria.
2. This has resulted in a virtually unlimited supply of the hormone and it has come to be used, not only to treat growth problems, but also to enhance athletic performance and in anti-ageing treatments.
What is Haemophilia A?
Sometimes referred to as classic haemophilia, is an inherited disorder which a blood clotting protein known as factor VIII is in poor supply or missing.
What do people with Haemophilia A suffer from?
People with the condition are unable to form blood clots adequately and are therefore at risk of life-threatening bleeding from injuries that would be trivial in people with normal blood clotting.
What problem did the production of factor VIII by recombinant DNA techniques overcame?
Two viral diseases that caused the deaths of many haemophiliacs all over the world were human immunodeficiency virus (HIV) and hepatitis C.
How has the use of Recombinant DNA tech assisted in the lack of factor VIII?
1. Factor VIII produced in this way has the added advantage that it is free of other plasma proteins that could cause an immune response or allergic reaction.
2. Recombinant factor VIII, one of the largest molecules synthesised to date, is cultured in mammalian cells and has been found to be highly effective in the control of excessive bleeding.
Why is the use of Recombinant DNA tech for vaccines not practical?
This is because they are very expensive as the genes for the desired antigens must be located, cloned and expressed efficiently in a new vector.
Define Gene Therapy.
Gene therapy aims to treat or cure genetic abnormalities by replacing faulty genes with healthy ones.
-It is a way of using the genes themselves as the treatment.
-Unlike most conventional medicines that treat the symptoms of a disease, gene therapy has the potential to correct the underlying cause because the faulty gene is replaced with a healthy one.
What is Cystic Fibrosis (CF)?
1. It is the most common life-threatening genetic disorder among Australians of European descent.
2. It mainly affects the lungs and pancreas but sometimes the live and reproductive organs.
3. CF is characterised by thick sticky mucus secreted by the mucous glands.
What happens if someone is affected with CF?
1. In the lungs, this mucus may clog the tiny air passaged and trap bacteria, making a person with CF susceptible to infection.
2. The pancreas is also affected, preventing secretion of enzymes required for digestion.
3. Therefore, people with CF frequently have problems with nutrition and need to take care with their diet.
When does CF occur?
CF results when an individual inherits the recessive allele for the condition from each parent.
Why is CF a logical choice for treatment using gene therapy?
- It is a single-gene disorder, and the most severely affected organ, the lung, is relatively easy to access to provide treatment.
-In addition, the disease is slow to progress, with the lungs of a newborn being virtually normal.
- This would enable gene therapy to begin before significant lung damage started to occur.
How does gene therapy assist sin Huntington's disease?
-It is another single-gene disorder and researches believe that gene therapy could be used to slow down or prevent its development.
-It is caused by mutation in a single gene on chromosome 4 called IT 15.