11/1/2009 Biology: 11.2 Human Applications Genetic Engineering Human Applications Genetic Engineering

11/1/2009 Biology: 11.2 Human Applications Genetic Engineering T he Human Genome Project:  The Human Genome Project is a research project linking 20 labs in six countries.  Teams of scientists in the project worked to identify and map all 3.2 billion base pairs of all the DNA that makes up the human genome.

11/1/2009 Biology: 11.2 Human Applications Genetic Engineering T he Human Genome Project:  One of the most surprising things about the human genome is the large amount of DNA that does NOT encode proteins.  In fact, only about 1 to 1.5% of the human genome is DNA that codes for proteins. Each human cell contains about 6 feet of DNA but less than 1 inch is devoted to exons.  (recall that exons are sequences of nucleotides that are transcribed and translated)

11/1/2009 Biology: 11.2 Human Applications Genetic Engineering T he Human Genome Project:  Exons are scattered about the human genome in clumps that are not spread out evenly among the chromosomes.  On most human chromosomes, great stretches of untranscribed DNA fill the chromosomes between the scattered clusters of transcribed genes.

11/1/2009 Biology: 11.2 Human Applications Genetic Engineering T he Number of Human Genes:  When they examined the complete sequence of the human genome, scientists were surprised at how few genes their actually are.  Human cells contain about 30,000 to 40,000 genes. This is only about double the number of genes in a fruit fly.  It is only about one quarter of the 120,000 genes scientists had expected to find.

11/1/2009 Biology: 11.2 Human Applications Genetic Engineering T he Number of Human Genes:  How did scientists make such a large mistake estimating the number of genes? —When scientists had counted messenger RNA (mRNA) they had found over 120,000. Each of these can in turn be translated into a unique protein. — Scientists had “expected” to find as many types of genes as their were different types of mRNA molecules.

11/1/2009 Biology: 11.2 Human Applications Genetic Engineering G enetically Engineered Drugs and Vaccines:  Drugs: Many genetic disorders and human illnesses occur when the body fails to make critical proteins.  J uvenile diabetes is such an illness. —The body is unable to control levels of sugar within the blood because a critical protein, insulin, cannot be made. —These failures can be overcome if the body can be supplied with more of the protein it lacks.

11/1/2009 Biology: 11.2 Human Applications Genetic Engineering G enetically Engineered Drugs and Vaccines: —Today, pharmaceutical companies worldwide produce these medically important proteins using bacteria and genetic engineering in combination.

11/1/2009 Biology: 11.2 Human Applications Genetic Engineering G enetically Engineered Drugs and Vaccines:  Today many genetically engineered medicines are used to treat everything from burns to diabetes.  Examples include: —Erythropoetin for anemia —Growth factors for treating burns, ulcers —Human Growth Hormone for growth defects —Insulin for diabetes —Interferons for viral infections and cancer —Taxol for ovarian cancer

11/1/2009 Biology: 11.2 Human Applications Genetic Engineering G enetically Engineered Drugs and Vaccines: V accines:  Many viral diseases, such as smallpox and polio, cannot be treated by existing drugs. Instead, they are combated by prevention through use of vaccines.  A vaccine is a solution containing all or part of a harmless version of a pathogen (disease-causing microorganism).  It is a weakened version of the disease; incapable of causing serious harm”

11/1/2009 Biology: 11.2 Human Applications Genetic Engineering G enetically Engineered Drugs and Vaccines: V accines:  When a vaccine is injected, the immune system reads the pathogen’s surface proteins and responds by making defensive proteins called antibodies. The immune system creates a defense system against this form of the disease.  In the future, if the same pathogen enters the body, the antibodies are now there to combat the pathogen and stop it’s growth before it can cause a disease. The immune system stays in place so when the flu or cold strikes in full force, the antibodies are already there to fight it before it can grow.

11/1/2009 Biology: 11.2 Human Applications Genetic Engineering G enetically Engineered Drugs and Vaccines: V accines:  Traditionally, vaccines have been prepared by either killing a pathogenic microbe or by making the microbe unable to grow.  The disease causing microbe is rendered into a “weakened form” ; strong enough to cause a reaction in the immune system but not strong enough to make the taker ill.

11/1/2009 Biology: 11.2 Human Applications Genetic Engineering G enetically Engineered Drugs and Vaccines: V accines:  This ensures that the vaccine itself will not cause the disease but only activate the antibodies to form.  With these types of vaccines there is always some small danger for getting sick as some people are more sensitive to the vaccine. Their threshold is lower.

11/1/2009 Biology: 11.2 Human Applications Genetic Engineering G enetically Engineered Drugs and Vaccines: V accines:  Vaccines made by genetic engineering avoid this danger and are less likely to risk infection to those who are extra-sensitive to the microbes.

11/1/2009 Biology: 11.2 Human Applications Genetic Engineering D na Fingerprinting:  Other than identical twins, no two individuals have the same genetic material.  Scientists use DNA sequencing technology to determine a DNA fragment’s nucleotide sequence.

11/1/2009 Biology: 11.2 Human Applications Genetic Engineering D na Fingerprinting:  Because the places a restrictive enzyme can cut depend on the DNA sequence, the lengths of the DNA fragments will vary between any two individuals.  A DNA fingerprint is a pattern of dark bands on photographic film that is made when an individuals DNA restriction fragments are exposed to an X-ray film.

11/1/2009 Biology: 11.2 Human Applications Genetic Engineering D na Fingerprinting:  Because these bandings are unique to every individual, they are like fingerprints.  The banding patterns from any two individuals can be compared to determine if they are related.  Because fingerprinting can be performed on a sample of DNA from blood, bone, or hair; DNA fingerprinting is used in forensics as a tool.

11/1/2009 Biology: 11.2 Human Applications Genetic Engineering D na Fingerprinting:  DNA fingerprinting can also be used to identify the genes that cause genetic disorders, such as Huntington’s Disease and Sickle cell Anemia.

11/1/2009 Computer Lab:  Use the internet to go online and write a one paragraph mini-report on the following topic: DO NOT COPY CUT OR PASTE:  How is DNA fingerprinting used in the science of modern forensics to solve crimes?

11/7/2009 Biology 11.3 Genetic Engineering in Agriculture Genetic Engineering in Agriculture

11/7/2009 Improving Crops  Farmers began primitive genetic breeding years ago by selecting seeds from their best plants, replanting them, and gradually improving the quality of their crops over time.  Today, we use genetic engineering to select and add characteristics and modify plants by manipulating a plant’s genes.

11/7/2009 Improving Crops  Genetic engineering can change plants in many ways; from making plants drought resistant to making plants that can thrive in different soils, climates or environmental conditions.

11/7/2009 Improving Crops  Genetic engineers have developed crop plants that are resistant to a biodegradable weedkiller called glyphosate. This enables farmers to spray their fields with glyphosate, kill all the weeds off, and leaves the crops unharmed.  Half of the 72 million acres of soybeans planted in the U.S. in 2000 were genetically modified to resist glyphosate.

11/7/2009 Improving Crops  Scientists have also developed crops that are resistant to certain insects by inserting specific genes into plants.  This added gene makes the plants produce proteins that make the plant unacceptable to the insects for a food source.

11/7/2009 More Nutritious Crops  Genetic engineering has been able, in many instances, to improve the nutritional value of many crops.  For example, in Asia, rice is a major food crop. Rice however is low in iron and beta-carotene.  Genetic engineers have modified rice in these countries by adding genes which boost the levels of iron and beta-carotene to the rice plants.

11/7/2009 Risks of Modified Crops  Risks: Many people, including many scientists, have expressed concern that genetically modified crops (GM crops) might turn out to be dangerous. —What kind of unforeseen negative affects might we experience from the new engineered crops?  Potential problems: We have already noted that crops such as soybeans have been genetically altered to make them resistant to the weedkiller glyphosate.  Scientists are concerned that the use of glyphosate will lead to weeds that are immune to this weedkiller. Than we will need to search for a new weedkiller and alter more crops to be resistant to it.

11/7/2009 Risks of Modified Crops A re GM crops harmful to the environment?  Will genes introduced into crops by genetic engineering pass on to wild varieties of plants? —This type of gene flow happens all the time between related plants. —In most crops however, no closely related wild version of the plant is nearby to take up the gene changes.  Some scientists fear that insect pests may become immune (by adapting) to the toxins that are genetically engineered in some plants. —This would lead to insect strains that are harder to kill as they would be immune to the genetically produced changes that were supposed to repel them.

11/7/2009 Gene technology in Farm Animals  F armers have, for generations, improved their stock of animals through selection of the best and cross breeding.  Now, many farmers use genetically- engineered techniques to improve their stock or their production.  Many farmers add growth hormone to the diet of their cows to increase the amount of milk their cows produce. The cow growth hormone gene is introduced into bacteria which is than added to the cow’s food supply.  This increases the amount of milk the cow produces.  Scientists have also boosted growth in pigs by adding growth hormone genes to the food that pigs eat. These procedures lead to faster growth and higher profits for farmers.

11/7/2009 Making Medically Useful Proteins  Another way in which gene technology is used in animal farming is in the addition of human genes to the genes of farm animals to produce human proteins in milk.  This is used for complex human proteins that cannot be made by bacteria through gene technology.  The human proteins are extracted from the animal’s milk and sold for pharmaceutical purposes. These animals are called transgenic animals because they have human DNA in their cells.

11/7/2009 Making Medically Useful Proteins: Cloning  More recently, scientists have turned to cloning animals as a way of creating identical animals that can make medically useful proteins.  In cloning, the intact nucleus of an embryonic or fetal cell is placed into a new egg whose nucleus has been removed.  The egg with the new nucleus is than placed into the uterus of a surrogate mother and is allowed to develop.

11/7/2009 Making Medically Useful Proteins: Cloning  Cloning from Adult Animals:  In 1997, the first successful cloning using differentiated cells from an adult animal resulted in a cloned sheep named Dolly.  A differentiated cell is a cell that has become specialized to become a specific type of cell.  In Dolly’s case; a lamb was cloned from the nucleus of a mammary cell taken from an adult sheep. Scientists thought that a differentiated cell would NOT give rise to an entire animal. The cloning of Dolly successfully proved otherwise.

11/7/2009 Making Medically Useful Proteins: Cloning  An electric shock was used to fuse mammary cells from one sheep with egg cells without nuclei from another sheep.  The fused cells divided to form embryos, which were implanted into surrogate mothers. Only one embryo survived the cloning process.  Born July 5, 1996; Dolly was the first cloned sheep, genetically identical to the sheep that had provided the mammary cell.

11/7/2009 Problems with Cloning:  Since Dolly’s birth in 1996, scientists have successfully cloned several animals.  Only a few of these cloned animals survive however. Many become fatally oversized.  Others encounter problems in development. For example, three cloned calves were born in March 2001, only to die a month later from immune system failure.

11/7/2009 The Importance of Genomic Imprinting  Technical problems with reproductive cloning lie within a developmental process that conditions egg and sperm so that the “right combination of genes” are turned “on” or “off” during early stages of development.  When cloned offspring become adults, a different combination of genes is activated.  The process of conditioning the DNA during an early stage of development is called genomic imprinting.

11/7/2009 The Importance of Genomic Imprinting  In genomic imprinting, chemical changes made to DNA prevent a gene’s expression without altering it’s sequence.  Usually, a gene is locked into the “off” position by adding methyl groups to it’s cytosine nucleotides.  The bulky methyl groups prevent polymerase enzymes from reading the gene, so the gene cannot be transcribed.  Later in development, the methyl groups are removed and the gene is reactivated.

11/7/2009 Why Cloning Fails:  Normal vertebrae development depends on precise genomic imprinting.  This process, which takes place in adult reproductive tissue, takes months for sperm and years for eggs.  Reproductive cloning fails because the reconstituted egg begins to divide within minutes. There is simply not enough time in these few minutes for the reprogramming to process properly.

11/7/2009 Why Cloning Fails:  Gene keys fail to become properly methylated, and this leads to critical problems in development.  Because of these technical problems; and because of ethical problems, efforts to clone humans are illegal in most countries.

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