Biology 3201 Genetics Unit #8

Transcription

1 Biology 3201 Genetics Unit #8 Diagnosis and Treatment of Genetic Disorders Genetic Engineering The Human Genome Project GMOs and GMFs Cloning Diagnosis of Genetic Disorders Detection of genetics disorders- Methods: 1. amniocentesis fluid from amniotic sac is removed with a needle. Karyotype is prepared along with other genetic tests to determine disorders. 2. CVS (chorionic villi sampling) cells are removed from the chorion or placenta and examined for genetic disorders 3. fetoscopy camera is used to view the fetus to look for physical abnormalities that may suggest genetic disorders 1

2 Diagnosis of Genetic Disorders 4. genetic markers these are indicators found in the DNA that indicate the inheritance of a defective gene or a gene causing a disorder. There are two types of markers: - linked markers: a known sequence of nucleotides located close to a gene that causes a disorder Gene specific marker: a sequence of DNA that is part of the gene itself Genetic markers are found using radioactive or fluorescent tags on complimentary DNA nucleotide sequences of the suspected marker Treatment of Genetic Disorders Methods: 1. genetic screening and prevention Blood and other biochemical tests are often done either at birth or prior to birth to determine genetic disorders Parents are often advised of options such as special diets, etc. they can place their children on. 2. surgery Surgery can repair some physical abnormalities caused by genetic conditions such cleft palate. 2

3 Treatment of Genetic Disorders 3. environmental control This is the controlling of the environment in which an individual with a disorder lives. Ex. People with Albinism (lack of melanin skin pigment) must avoid sunlight. These people usually are fully clothed all the night and go out at night, etc. 4. gene therapy A procedure in which normal or modified genes are transferred into defective cells of an individual. The new genes should cause the cells to work normally and fix the genetic disorder. Ethical questions arising from the use of gene therapy Are we playing God? Who gets the modified genes and who does not? For what conditions are the genes produced/used? What cost and who pays for the procedure? 3

4 Genetic Engineering Restriction Enzymes Genetic engineering: the manipulation of an organism s genetic material to modify the proteins it produces. Techniques involved: 1. restriction enzymes: these enzymes such as restriction endonucleases are used to cut DNA into shorter pieces. Each fragment has sticky ends (short segments of unpaired DNA bases) at each end of the fragment. Restriction Enzymes 4

5 Genetic Engineering Recombinant DNA 2. recombinant DNA: a new segment of DNA made by combining or joining DNA from two different sources. DNA which you want to insert into a new genome is cut using restriction enzymes, along with the original DNA The sticky ends of the inserted gene pair with sticky ends of original DNA Recombinant DNA 5

6 Genetic Engineering DNA Amplification (cloning vectors) 3. DNA Amplification The process of generating a large sample of DNA from a single gene or DNA fragment Two methods used in this process (1) cloning vectors: use of a bacteria or virus to produce many copies of a foreign DNA sequence. Foreign DNA is spliced into the DNA of either a virus or bacteria and they are allowed to reproduce. The DNA is then harvested from the bacteria or virus at a later time. 6

7 Genetic Engineering DNA amplification (PCR) (2) Polymerase Chain Reaction (PCR): an automated method of reproducing DNA by using enzymes such as DNA polymerase and primers Steps: DNA section is placed in a solution of free nucleotides (the free nucleotides are used to make copies of the DNA section) Heated to open the double helix DNA polymerase is added and DNA replication occurs Cycle is repeated several times End result is lots of DNA sequence that is wanted 7

8 Genetic Engineering Gel Electrophoresis and DNA Sequencing Fragments of DNA are separated according to their mass and electrical charge On one end of a gel plate a sample of DNA fragments is placed. The gel is given an electric current causing it to become polarized on the other end. The fragments are negatively charged and they are attracted to the other end of the gel. The fragments move according to their mass. The smaller fragments move more quickly toward the opposite end of the gel. After a while a characteristic pattern of bands emerges. This is known as the DNA FINGERPRINT of a person DNA sequencing: the process of reading DNA fragments so as to determine the exact sequence of base pairs in a sample of DNA 8

9 9

10 The Human Genome Project A 13 year project aimed at sequencing the entire human genome. Several scientists from around the world worked on the project Completed in billion base pairs were sequenced Why was it done? Scientists thought that id we could know the entire sequence of the human genome we could determine and cure disorders that affect the human population Our DNA could be compared to other organisms Major Findings of the Human Genome Project (1) 99.9 % of all human DNA is identical (2) there are approximately genes in the human population. Much less than the expected 100,

11 Risks and Benefits of the Human Genome Project Risks Privacy all of genome is known, so your DNA is not so unique anymore Financial if genetic disorders can be determined to exist in population, can insurance be cancelled, denied, etc. Employment,??? Ethical should we be playing God? Benefits Knowledge of predisposition to disease we know about the predisposition to disease so treatments and/or preventions can be implemented Analysis of diseases diseases that are known can be analysed and preventions/cures created Genetically Modified Foods and Organisms GMO = genetically modified organisms GMF = genetically modified foods Most GMFs and GMOs are transgenic (genes are moved/altered) Examples Herbicide resistant corn Cows with high milk production Golden rice (high amounts of vitamin A and iron) Transgenic salmon Insulin producing bacteria PCB eating bacteria Oil eating bacteria 11

12 Risks/Benefits of GMOs and GMFs Risks More herbicides used If genes spread to wild organisms could affect biodiversity Could create superbugs (immune to pesticides) Benefits Alleviate world hunger Employment for more farmers, etc. Cloning Cloning: the production of an organism that is genetically identical to another. Ex. Dolly the sheep Benefits and Risks Elimination of disease Speed of production Manipulation of traits Reducing genetic variety (all are alike) Embryo destruction and use ethics??? 12

13 Therapeutic vs. Reproductive Cloning Therapeutic cloning: the culturing of human cells for use in treating medical disorders Ex. Using cloned pancreatic cells to cure diseased cells of the pancreas Reproductive cloning: the development of a cloned embryo for the purpose of creating an entire organism Ex. Dolly the sheep 13