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a. Cloning is the production of identical offspring. A clone is an animal that is genetically identical to its donor ‘parent’. This can be achieved using cells derived from a microscopic embryo, a foetus, or from an adult animal. Cloning from adult animals was introduced to the public in 1997 when scientists announced the birth of Dolly, the first animal cloned in this way. There have now been hundreds of clones produced from skin cells taken from adult sheep, cattle, goats, pigs and mice. The real key to cloning an adult animal is the ability to reprogram the skin cell nucleus and cause it to begin developing as if it was a newly fertilized egg.
Entire frogs and mice have been successfully cloned from embryonic cells; the first animal cloning was carried out by Briggs and King in 1952, who successfully cloned northern leopard frogs. British researchers led by Ian Wilmut achieved the first success in cloning an adult mammal in 1996. Having already produced clones from sheep embryos, they were able to produce a lamb (Dolly) using DNA from an adult sheep. However, the success rate was extremely low, numerous embryos were aborted when it was identified that they were growing irregularly, others were still born or were naturally miscarried by the ‘mother’, probably due to deformities.
The way a clone is produced involves the following five basic steps and requires specialized microsurgery tools:
a. Enucleation of the recipient egg.
b. Transfer of the donor cell into the recipient egg.
c. Fusion of the donor cell to the recipient egg.
d. Culturing the resulting cloned embryo in the incubator.
e. Transferring the developing embryo into the reproductive tract of a surrogate mother
The most common method currently used for cloning is Somatic Cell Nuclear Transfer (SCNT), which was first explored by Hans Spemann in the 1920's to conduct genetics research, nuclear transfer is the technique currently used in the cloning of adult animals. All cloning experiments of adult mammals have used a variation of nuclear transfer.
A somatic cell is any cell other than a sperm, egg, or cell that gives rise to a sperm or egg. Nuclear transfer requires two cells, a donor cell and an oocyte. The nucleus of the egg (containing its DNA) is removed and replaced with the nucleus (and its DNA) of a somatic cell (such as skin or blood) from the recipient. Research has proven that the egg cell works best if it is unfertilized, because it is more likely to accept the donor nucleus as its own. The egg cell must be enucleated, which eliminates the majority of its genetic information. The donor cell is then forced into the Gap Zero, or G0 cell stage, a dormant phase, which causes the cell to shut down but not die. In this state, the nucleus is ready to be accepted by the egg cell. The donor cell's nucleus is then placed inside the egg cell, either through cell fusion or transplantation. The egg cell is then prompted to begin forming an embryo. The embryo is transplanted into a surrogate mother if stem cells are not the goal. If all is done correctly, occasionally a perfect replica of the donor animal will be born.
b. In 1973, scientists made a discovery that had the potential to change the world we live in forever; they discovered Genetic Modification, the alteration of genes inside a living organism. This of course could be used on humans or animals but as soon as this discovery was made safety precautions were put into place to stop people using this new technology in the wrong way. The secret to genetic modification of genes lies in the plasmid. A plasmid is a ring of DNA inside bacteria and can be used to change the genetic message inside the bacteria. For example if you were to want to create insulin you would extract the insulin producing gene from the pancreas cell of a human and cut open the plasmid and insert it the gene. This new DNA created is called recombinant DNA. The bacteria would then go on to produce human insulin.
The primary aim of genetic modification is to introduce, improve or delete particular characteristics of organisms. This can be achieved through the manipulation of genes or ‘gene therapy. Genes are functional parts of DNA. Genetic engineering usually involves the insertion of a gene or genes from one species into another species; this manipulation of DNA is permanent. This manipulation is the basis of how this technology works it can also be transferred to foods. Scientists are now looking how they can genetically modify food in the world to make it better and hardier than the food nature produces. Genetic modification has the potential to offer very significant improvements in the quantity, quality, and acceptability to our life and standard of living.
In many supermarkets today, many vegetables, which would normally not grow in certain countries, can be bought easily. Plants are cloned after genetic (DNA) modification. These fruit and vegetables are then increasingly cloned to make them reasonably priced and to be able to deal with the demand for them. This allows consumption and greater profits, which in turn pushes our economy.
Animals such as sheep cloned in order to increase wool production. While the best sheep produce wool and cloned to keep up the quality. A small number of sheep might also be cloned in order to produce meat This not only helps to increase the amount of milk and beef produced but also the amount of that will be bought and will assist another economical boost which mankind benefits from.
These are some effects of genetic modification:
GM Crops: A genetically modified food is a food product containing some quantity of any genetically modified organism (GMO) as an ingredient.
Gene Therapy: newly developing technique used to treat inherited genetic diseases. The medical procedure involves adding a healthy gene into the cells of a patient's body, overcoming the effects of the defective gene.
How does genetic modification effects quality of life and standard of living? Over the past few years, the quality of life and standard of living has been affected by the use of genetic modification all over the world. Genetic modification has the potential to offer very significant improvements in the quantity, quality, and acceptability to our life and standard of living.
These are same examples:
Tomatoes
- You go shopping for tomatoes, what do you look for in the ones you buy? Better colour? Better taste? Or just better smell? Well, tomatoes have been genetically modified so that they grow slower resulting in better colour and taste.
Grain & Fruit Alteration
- Many grain plants have been genetically modified to resist different viruses. Farmers are then able to produce more crops since not nearly as many plants are dying from certain viruses. Many fruits have also been genetically altered.
Genetically modified foods and crops have benefits to mankind but there are potential drawbacks to their widespread use which include an example from the USA, where Laboratory tests have shown that pollen from GM maize in the US damaged the caterpillars of the Monarch butterfly. This is a case of damage to a single species, but it does show that genetically-modified organisms could have the potential to do unexpected harm to other plants and animals. In the end, this could lead to a loss of biodiversity and to certain animal and wild plant species effectively being rendered extinct. Furthermore, where test crops have been planted in the UK, there is a definite danger of cross-contamination with wild or non-GM plant strains. Even with very strict controls in place, it is impossible to prevent pollen from travelling on the wind from GM crops to other, possibly organic versions of the same crop being grown nearby. Pollen could also be carried by insects. This could mean that in the end, all our food crops could contain a proportion of genetically-modified elements, and we as consumers would lose our right to choose whether to eat GM foods or not.
c. DNA fingerprinting is a technique used to identify individual organisms based upon the uniqueness of their DNA pattern. It was discovered by Dr Alec Jefferies. No two people (except for identical twins) have exactly the same DNA base sequence. 99% of DNA in all humans is the same. However, the 1% that is highly variable allows scientist to distinguish the identity of a sample, when the ‘donor’ is found.
The DNA alphabet is made up of four building blocks-A, T, C, and G called base pairs. The order in which these are linked together determine the meaning or function of the genes they code for. However, not all DNA contains useful information. A large amount of it is ‘junk’ which is not translated into useful proteins. In the non-coding regions of the genome, sequences of DNA are frequently repeated giving rise to variable number tandem repeats (VNTRs). The number of repeats varies from one person to another and can be used to produce their genetic fingerprint. For example one person might have the bases CCCT repeated four times, while another person may have the same bases repeated seven times. Researchers can determine the number of VNTR repeats in order to come up with an individual’s DNA profile using a method called Restriction Fragment Length Polymorphism (RFLP) analysis.
The first step is to collect DNA sample. DNA must first be recovered from the cells or tissues of the body in order for the other procedures to take place. Only a small amount of tissue - like blood, hair, or skin - is needed. Next, a method called Polymerase Chain Reaction (PCR) must be used to amplify samples that contain tiny amounts of DNA. As it is difficult to work with such small samples, PCR makes it much easier to work. The enzyme that is used in copying DNA is DNA polymerase, extracted from bacteria (Thermus aquaticus) living in the superheated waters of hot springs. When DNA is heated to about 80 degrees Celsius, the DNA unzips. Since, the enzyme is extracted from an organism that is adapted to such high temperatures, the enzymes are not destroyed and continue to work. The unzipped, single strands act as templates. Primers designed to base-pair with the ends of the DNA strand will be added. The mixture is cooled to about 30 degrees Celsius and this promotes base-pairing between DNA strand and primers. The DNA polymerase recognizes the primers as Start tags and they assemble complementary sequences on the strands. This doubles the number of identical DNA fragments. By repeating this procedure over and over again, a very large DNA sample can be obtained. The next step is to cut the DNA into smaller, more manageable pieces. This is done using special enzymes called restriction enzymes. For example, an enzyme called EcoR1, found in bacteria (Escherichia coli), will cut DNA only when the sequence GAATTC occurs. Cutting DNA with a restrictions enzyme breaks the chromosomes down into millions of differently sized DNA fragments. It is important to select an enzyme that does not cut within any of the VNTR regions that are being studied. For RFLP analysis the enzymes chosen will ideally cut close to the end, on the outside of the tandem repeat region. Once this is done, the DNA fragments are then sorted by size using gel electrophoresis. The DNA is poured into a gel, such as agarose, and an electrical charge is applied to the gel. When an electrical current is applied, one end of the gel takes on a negative charge and the other end takes on a positive charge. DNA has a slightly negative charge (the phosphate groups are negatively charged) and as a result of this, the pieces of DNA will be attracted towards the positively charged part of the gel. The smaller pieces will be able to move more quickly and thus further towards the positive pole than the larger pieces. The different-sized pieces of DNA will therefore be separated by size, with the smaller pieces towards positively charges area at the top and the larger pieces towards the negatively charged area near the bottom of the agarose. Next, DNA pieces need to be transferred to a nylon sheet. This is done by placing the sheet on the gel with the distribution of DNA and soaking them overnight. Adding radioactive or colored probes to the nylon sheet produces a pattern called the DNA fingerprint. Each probe typically sticks in only one or two specific places on the nylon sheet. The final DNA fingerprint is built by using several probes simultaneously. It resembles the bar codes.
Forensic scientists make use of genetic fingerprinting to identify persons who have committed a crime, during which they leave behind a genetic sample of themselves. This sample can be compared to National or International Databases. Various people have tried to argue that keeping an individual’s details on this database is an invasion of privacy or an infringement of their human rights, the counter to this is that the only people that have anything to worry about any infringement is those that have done something wrong. Further uses of genetic fingerprinting is identifying human remains that have been that destroyed that they do not bear any visible resemblance to the deceased, this was used extremely successfully after 9/11 and in the hunt for Saddam Hussein, who reportedly used numerous ‘body doubles’ to assist with his ‘security arrangements’. When Saddam Hussein was captured the Allies knew they had the right man. Genetic fingerprinting can use be used to assist in paternity cases, where there is a question over who is the father of a child.
d. Research on stem cells is advancing knowledge about how an organism develops from a single cell and how healthy cells replace damaged cells in adult organisms. This promising area of science is also leading scientists to investigate the possibility of cell-based therapies to treat disease, which is often referred to as regenerative or reparative medicine. Stem cells are one of the most intriguing areas of biology today. But like many expanding fields of scientific investigation, research on stem cells raises scientific questions as rapidly as it generates new discoveries or explanations.
Stem cells have two important characteristics that distinguish them from other types of cells. First, they are unspecialised cells that renew themselves for long periods through cell division. The second is that under certain experimental conditions, they can be induced to become cells with special functions such as the beating cells of the heart muscle or the insulin producing cells of the pancreas. Scientists primarily work with two kinds of stem cells from animals and humans: embryonic stem cells and adult stem cells, which have different functions and characteristics that will be explained in this document. Scientists discovered ways to obtain or derive stem cells from early mouse embryos more than 20 years ago. Many years of detailed study of the biology of mouse stem cells led to the discovery, in 1998, of how to isolate stem cells from human embryos and grow the cells in the laboratory. These are called human embryonic stem cells. The embryos used in these studies were created for infertility purposes through in vitro fertilization procedures and when they were no longer needed for that purpose, they were donated for research with the informed consent of the donor. Stem cells are important for living organisms for many reasons. In the 3- to 5-day-old embryo, called a blastocyst, stem cells in developing tissues give rise to the multiple specialized cell types that make up the heart, lung, skin, and other tissues. In some adult tissues, such as bone marrow, muscle, and brain, discrete populations of adult stem cells generate replacements for cells that are lost through normal wear and tear, injury, or disease. It has been hypothesized by scientists that stem cell technology may be used in the future for treating diseases such as Parkinson's disease, diabetes, and heart disease.
Bibliography
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