Genetic Engineering and Other Aspects of Biotechnology

Transcription

1 Genetic Engineering and Other Aspects of Biotechnology IB Biology Outcomes Outline the use of polymerase chain reaction (PCR) to copy and amplify minute quantities of DNA State that, in gel electrophoresis, fragments of DNA move in an electric field and are separated according to their size State that gel electrophoresis of DNA is used in DNA profiling Describe the application of DNA profiling to determine paternity and also in forensic investigations Analyse DNA profiles to draw conclusions about paternity or forensic investigations Outline three outcomes of the sequencing of the complete human genome State that, when genes are transferred between species, the amino acid sequence of polypeptides translated from them is unchanged because the genetic code is universal Outline a basic technique used for gene transfer involving plasmids, a host cell (bacterium, yeast or other cell), restriction enzymes (endonucleases) and DNA ligase State two examples of the current uses of genetically modified crops or animals Discuss the potential benefits and possible harmful effects of one example of genetic modification Define clone Outline a technique for cloning using differentiated animal cells Discuss the ethical issues of therapeutic cloning in humans. Copying and Amplifying DNA PCR or polymerase chain reaction is a method used by scientists to produce millions of copies of a sequence DNA. This can be completed in two hours and means that scientist do not have to use bacteria to amplify DNA. DNA from very small samples such as semen, blood, tissues, or even from specimens that have been dead for a long time can be amplified using PCR. PCR Funny Videos s Dow Gel Electrophoresis Gel electrophoresis is used to separate mixtures of proteins, DNA, or other molecules that have a charge. Enzymes are used to chop DNA into smaller fragments and the DNA fragments are placed on a thin sample of gel and an electrical charge is applied to both ends of the gel. This is done by placing a positive electrode on one end of the gel and a negative electrode on the other end.

2 The particles will move based on their charge towards one electrode or the other. The result is a picture of bands of DNA. The rate at which the DNA particles move is dependent upon the size and charge of the DNA molecule. The smaller and highly charged molecules will move farther and faster than larger, less charged molecules. DNA Profiling The process of gel electrophoresis produces a DNA profile of the organism which can be used to compare and contrast DNA sequences. The process of matching the unknown sample of DNA with a known sample is called DNA profiling. The pattern of bands produced is specific to the individual involved and it is highly unlikely to be the same for any two individuals. DNA Profiling DNA profiles can be used in paternity suits where there is an unknown parent. By comparing the DNA profiles created through gel electrophoresis parentage can be proved. DNA profiling can also be used in criminal investigations (murder or rape) when there is DNA left at the scene of the crime. A DNA sample can be taken from the suspect, profiled and compared to the DNA found at the scene.

3 Problems... One difficulty of DNA profiling can be that cross contamination of the DNA sample could alter the results. How else is it used? DNA profiling is also used to identify relationships between organisms to see which individuals are related. Ecologists use DNA profiling to help establish an understanding of social relationships, migrating patterns and nesting habits. Similar DNA? The Human Genome Project The human genome project launched in 1990 and it has been a worldwide collaborative effort to sequence the entire human genome. Sequencing the human genome will make it easier to study how human development is affected by genes. The project succeeded in 2003 and now scientists are attempting to which sequences represent genes and what those genes do.

4 Knowing the human genome could allow for easier identification and treatment of genetic diseases. Drugs to treat disease in humans could be manufactured based on the DNA base sequence of genes or the structure of the proteins coded for by those genes. The Human Genome project will also give us new information about the origins, evolution, and migrations of the human species. Universal Genetic Code Gene transfer involves the removal of a gene from one organism and placing it into another. The genetic code is universal which means it is the same for all living things. In other words, a gene codes for the same polypeptide whether it is a human cell, bacterial cell, or any other type of cell.

5 Gene Transfer Gene transfer is a process often called genetic modification and any organism that has had genes transferred to them are referred to as genetically modified organisms (GMO) or transgenic organisms. One technique often used in gene technology is the cloning of DNA inside a bacterium, most often E. coli. This can be done because the genetic code is universal therefore it can be transferred from one organism to another. The following diagram shows an overview of gene cloning using a bacterium plasmid. Genetically Modified Crops & Animals Plants and animals that have been genetically modified are known as GMO s. Tomato plants have been genetically modified to become more tolerant of salt in the soil. There is hardly anything that farmers can plant that tolerates salt so it gives farmers a crop to plant in their soil with a higher salt content.

6 Some tomato plants (cherry tomatoes) have also been genetically modified to delay the ripening process which allows them to survive the harvesting and shipping period and ripen reaching full flavor in time for sale. Resistance to Herbicides Some plants have had genes introduced to them that allow them to thrive even when they are exposed to herbicides meant to kill weeds. Animals Some animals can be used as a pharmaceutical factory to produce large amounts of rare biological substances needed for medicinal purposes. Sheep are often used to carry a gene for a human blood protein needed for blood clotting. The sheep secrete the factor IX in their milk which can then be purified. Pros and Cons of Gene Modification Gene transfer can be regarded as potentially harmful. There is a lot of concern surrounding the release of the GMO s into the environment. They could spread and compete with or potentially wipe out the naturally occurring varieties. There is also concern that the engineered genes could cross species barriers.

7 One benefit of gene modification is that it provides more specific or less random breeding than that of the more traditional methods. Example Maize crops (corn) is a good example of gene modification that has many potential benefits and harmful effects. The crops are often damaged by corn borer insects so a gene from a bacterium has been transferred into the maize. This gene codes for a bacterial protein called Bt toxin that kills corn borers who feed on the maize. Possible Benefits Possible Harmful Effects Less pest damage would lead to higher The Bt toxin or the bacterial DNA found crop yields. This could help reduce food in the genetically modified maize could shortages. be harmful to humans or animals. Higher crop yields means less land needs to be used. Some land could then become wildlife conservation areas. Insects other than the corn borers could be killed. The toxin is found in maize pollen which is blown onto plants surrounding the crops. Any insects that feed on the wild plants could be harmed. The gene transfer would reduce the amount of insecticide sprays which are expensive and harmful to farmers and wildlife. The spread of the pollen containing the Bt gene could potentially change the wild plants in the surrounding area. Cross pollination in some plants but no others means that there would be a struggle for the plants without the Bt toxin to survive. Clones Clones are a group of genetically identical organisms or a group of cells artificially derived from a single parent cell that has already differentiated. 3 naturally occurring examples of clones: Monozygotic twins, Plant cuttings, Asexual reproduction. Cloning using differentiated cells

8 Cloning Arguments Humans? for cloning in humans Already happens naturally when identical twins are formed; not a new phenomenon. Arguments against cloning in humans There could be psychological problems of identity or individuality among clones. Click and Clone Game ning/clickandclone/ When screening for genetic diseases the cloning of embryos would make the process easier. There is a lot of potential for suffering because cloning using differentiated cells carries a high risk of fetal abnormalities and a high rate of miscarriage. Couples who cannot have children on Due to the fact that the DNA extracted their own could increase their chances of from the differentiated cells has already success with IVF if their embryos are begun the ageing process the cloned cloned human may grow older faster than usual. What do you think about cloning humans?