Genetic Engineering and Biotechnology Definition Genetic engineering the
Genetic Engineering and Biotechnology
Definition Genetic engineering – the direct manipulation of genes for practical purposes. ✄ Ex: “Improving” plants and animals by adding genes from other species. ✄ Rice with new genes for vitamins from bean. ✄ Cows with extra copies of genes for milk. ✄ Glow-in-the-dark fish (using genes from jellyfish) for the home aquarium. ✄ Pink-haired poodles for the pet market.
Polymerase chain reaction PCR is a technique by which any piece of DNA, however tiny, can be quickly amplified (copied many times) without using living cells. ✄ ✄ Amplify 40, 000–year-old wooly mammoth DNA*. Amplify tiny amounts of DNA at a crime scene. Amplify embryonic DNA for pre-natal testing. Amplify DNA from difficult-to-detect viruses like HIV. *
Polymerase chain reaction PCR consists of a series of 20 to 40 repeated temperature changes called cycles; each cycle doubles the amount of DNA. ✄ Step 1: Denaturation heat to 94 -98°C for 30 sec. It breaks the hydrogen bonds.
Polymerase chain reaction PCR steps (cont’d) . ✄ Step 2: Extension/elongation DNA polymerase synthesizes a new DNA strand complementary to the DNA template strand by adding nucleotides that are complementary to the template.
Polymerase chain reaction PCR steps (cont’d) . ✄ The procedure repeats for 20 40 cycles, making billions of copies automatically. PCR machine
Gel electrophoresis To learn the characteristics of DNA and protein samples, the material must first be separated. ✄ In gel electrophoresis, electrophoresis fragments of DNA or proteins move in an electric field and are separated according to their size. Horizontal separation Vertical separation
Gel electrophoresis Separation of DNA using an electric current. Small-sized pieces move faster through the gel.
DNA profiling Gel electrophoresis of DNA is used in DNA profiling ✄ Large portions of any single person's DNA are the same as every other person's since they code for species-specific traits such as feet, ears, etc. ✄ Other fragments are unique to the individual. These fragments are called polymorphisms because they vary in shape from person to person. ✄ DNA profiling is the process of separating an individual's unique polymorphic fragments from the common ones to identify one individual.
DNA profiling can be used to determine paternity and also in forensic investigations. Match polymorphisms. Profile obtained from blood Profile obtained from convicted left at scene of an assault. offender and entered in CODIS* Unique fragments of DNA are compared. *Combined DNA Index System – a computerized data base of offenders
DNA profiling can be used to determine paternity, and also in forensic investigations. Social implications: ✄ Identity issues for children who discover a biological father is different from whom was expected. ✄ Fatherhood issues for an unmarried teen – when a guy learns he is or is not the father. ✄ When responsibility for a crime is confirmed or denied decades after the crime was committed.
Sequencing the human genome The human genome has recently been completely decoded (or sequenced). The genome is the set of all the genes that produce a human being. ✄ As we identify the similarities - and the differences - among the genes of mammals and other organisms, we will gain valuable new insights into human evolution.
Sequencing the human genome The human genome has recently been completely decoded (or sequenced). The genome is the set of all the genes that produce a human being. ✄ The genetic code can be used to identify diseaseassociated genes and eventually indicators of what drugs can be effective against the illness.
Sequencing the human genome The human genome has recently been completely decoded (or sequenced). The genome is the set of all the genes that produce a human being. ✄ Parents can possibly choose to select a baby’s characteristics (as in the movie GATTACA): improved physical stamina and lifespan, athleticism, height, hair color, etc.
Genetic Engineering and Biotechnology
Universal genetic code When genes are transferred between species, the amino acid sequence of polypeptides translated from them is unchanged because the genetic code is universal. ✄ DNA triplets code for the same amino acids in every organism. This supports theory of evolution: one common ancestor.
Gene transfer techniques DNA technology makes it possible to clone genes. a) A foreign gene is inserted into a bacterial plasmid, producing recombinant DNA - artificial DNA from 2 sources. Overview Plasmid Transformation b) This recombinant plasmid is returned to a bacterial cell. Every time this cell reproduces, the recombinant plasmid is replicated as well (cloned) and passed on to its descendents. ✄ Clone – an identical copy of the original.
Gene transfer techniques Restriction enzymes are used to make recombinant DNA. ✄ Restriction enzymes cut DNA molecules at specific locations. Ex: Eco. R 1 cuts at 3'-CTTAAG- 5', wherever it occurs. ✄ They cut in staggered way creating single-stranded “sticky” ends. These will form hydrogen bonds with complementary single-stranded stretches on other DNA molecules.
Gene transfer techniques Cloning a gene into a bacterial plasmid requires 5 steps. 1) Isolate the plasmid and the foreign gene. ✄ Plasmids are small circular bits of extra DNA found in bacteria that often confer resistance to toxins in environments. ✄ A variety of artificial plasmid vectors have been constructed for this purpose with special sites for restriction enzymes and resistance to antibiotics. The “gene of interest” is the foreign DNA to be inserted into the host.
Gene transfer techniques Cloning a gene into a bacterial plasmid requires 5 steps. 2) Use a restriction enzyme to cut out the gene and to open the plasmid (producing sticky ends on each), mix them, then use DNA ligase to splice the sticky ends together.
Gene transfer techniques Cloning a gene into a bacterial plasmid requires 5 steps. 3) Put the recombinant plasmid into bacteria (the process of transformation – changing an organism by adding foreign DNA). ✄ Mix the plasmid DNA and the bacteria under the proper conditions, and a small amount of DNA will pass through the bacterial cell wall.
Gene transfer techniques Cloning a gene into a bacterial plasmid requires 5 steps. 4) Clone the cells - use a growth medium containing the selected antibiotic. ✄ Only cells with the antibiotic resistance (on the plasmid) can grow. Instead of looking at millions of colonies, only a few will grow on the culture medium. 5) Identify the clones. Resistant cells should contain the foreign DNA.
GM crops and animals Current uses of genetic modification techniques: ✄ Grow GM bacteria for production of proteins. ✄ Transfer genes into other organisms. Note the applications
GM crops and animals Genetically modified crops Benefits: ✄ Plants could make their own nitrogen fertilizer by adding genes from nitrogen-fixing bacteria that make NH 4 from N 2 in the atmosphere. ✄ Resistance to an herbicide (weed killer) called glyphosate was brought into cotton and other plants from bacteria. ✄ Resistance to insects – a bacterial protein that kills insects was used to transform crop plants. If insects (like caterpillars) eat the plant they die, but humans are not affected. + All of these uses would save farmers money and reduce environmental pollution.
GM crops and animals Genetically modified crops Hazards: ✄ Introduced genes could “escape” into the environment and have unintended effects: - Weeds could acquire the gene and become “super weeds”. - Pollinators (bees and butterflies) could die as well as the pests, or herbivores could be affected. ✄ Humans could be affected (allergies) - Many European governments will not accept American plant products for fear that they are GM (economic issues) with unknown health risks.
GM crops and animals Genetically modified crops Ethics of use: ✄ Should humans be changing other creatures just to suit our purposes? ✄ How do we assess the risks and avert a disaster? ✄ Who is responsible when something goes wrong? Who cleans up the mess? ✄ In Europe some people take it upon themselves to destroy fields of GM crops.
Cloning animal cells Definition: Clone – a group of genetically identical organisms, or a group of cells derived from a single parent cell. A technique for cloning using differentiated animal cells
Cloning animal cells Reasons for cloning animals: ✄ Produce a group of horses, cows, etc. with superior qualities. ✄ “Bring back” beloved pets. ✄ Bring extinct animals back to life. Ex: the Tasmanian wolf, hunted to extinction >100 years ago. Dolly, the ewe: the cloned cells were taken from her udder.
Therapeutic cloning Definition: Therapeutic cloning – the creation of an embryo to supply embryonic stem cells for medical use. ✄ A human embryo is produced and destroyed. Is that murder? ✄ A life can be saved when new organs are produced in this way, and there are no problems with rejection.
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