Genetic Engineering

Polymerase Chain Reaction (PCR) Fig in text a technique for quickly cloning a particular piece of DNA in the test tube (rather than in living cells like E. coli). Very useful if only have small quantities such as blood or semen. Use temperature changes to separate the DNA strand, add primers, polymerase and ta-dah... new strand is made.

Gel Electrophoresis and DNA Profiling. Fig 16.2 in text Method using electricity to separate fragments of DNA –fragments are made by using restriction enzymes Large segments of DNA (negatively charged) can’t move through gel very far while small ones can. In agarose gels, fragments of DNA from about 200 to 50,000 bp can be separated The results from electrophoresis can be used for DNA profiling/fingerprinting – using the patterns of bands of DNA to identify and compare individuals. –Useful for identifying rapists, criminals, determine paternity, determine relatives...

Genetic Screening The testing of an individual for the presence or absence of a gene Advantages –fewer children with genetic diseases are born (a couple doesn’t reproduce or only selects “good” embryos for implantation) –confirmation of animal pedigrees –if genetic diseases can be found early enough, treatments can be given to prevent all or some of the symptoms of the disease

Disadvantages –frequency of abortion may increase –harmful psychological effects –creation of a genetic underclass (refused jobs, insurance, spouse...)

Genetically Modified Organisms organisms that have had genes from a different organism transferred to them examples –crops resistant to herbicides (but the weeds are not) –insulin gene from humans is put in the plasmid of E. coli which then makes insulin –a bacterium gene that codes for a protein called Bt toxin that kills moths that bore through corn is transferred to the DNA of corn

Benefits –less pest damage –less land needed for crops –less use of insecticides Harmful effects –humans/animals my be harmed by toxin –other non-corn eating insects could be killed by pollen from the corn –cross-pollination could spread the toxic gene to some wild corn that would then have an advantage over other natural species

Gene Therapy the treatment of diseases by altering the defective genotype of the organism example: SCID (severe combined immune deficiency) –screening before birth can show SCID –the enzyme ADA that is necessary to make healthy lymphocytes is not made lymphocytes, a type of white blood cell, are made from blood forming precursors, or "stem," cells in the bone marrow

–the allele that codes for ADA is obtained and the gene is inserted into a retrovirus –the retroviruses insert the gene into the stem cells’ chromosomes –new stem cells containing working ADA gene are injected into the person

Clones a group of genetically identical organisms or cells artificially derived from a single parent cell ex) Dolly –cells were taken from a donor sheep and the nucleus removed –eggs from another sheep were taken and the nuclei were removed –donor cells and nuclei were fused together using electricity and then developed into embryos that were implanted into a surrogate mother –a lamb was born (Dolly) that was genetically identical to the donor sheep

ethical issues in humans –Pros happens naturally with twins infertile couples might have better chance of success with cloning of embryos –Cons psychological/identity problems for groups of genetically identical people cells used in cloning have already begun to age and therefore cloned humans may age faster lead to selection of a super-race of those fit to be cloned