Chapter 23 - Biotechnology Flashcards
Define genome.
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.
- Each nucleotide has a different base - adenine, cytosine, guanine or thymine.
Explain the process of DNA sequencing.
- In building a sequence, each new nucleotide is bonded to the hydroxyl group (OH) of the previous nucleotide.
- In Sanger’s method of determining a DNA sequence, synthetic nucleotides that lack this OH group are added to the growing strand.
- The synthetic nucleotides stops the elongation of the sequence because there is no OH group for the next nucleotide to attach to.
- 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?
- Spastic Paraplegia - inherited disorder that causes progressive limb weakness and stiffness, often resulting in paralysis.
- 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.
- 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?
- 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?
Not necessarily.
- 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 .
- By using DNA polymerase, the original molecule of DNA is replicated doubling the number of DNA molecules.
- Each molecule is then replicated in a second sequence of replication, resulting in four times the number of original molecule.
- 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 ?
- Sickle cell anaemia
- Phenylketonuria (PKU)
- Cystic Fibrosis
- Viral disease
- 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.
