Human Genetic Diseases non mutation

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1 Page 1 of 10 Human Genetic Diseases non mutation These are diseases that normally occur because of gene inheritance rather than mutations. 1. Autosomal Recessive Inheritance This is the inheritance of a disease through a recessive allele. In order for the person to have the condition they would have to be homozygous. Ex: a. Tay Sachs disease A disease where a recessive allele causes an enzyme to be lacking in the lysozomes of brain cells. Lipids build up inside the cell and destroys it. Patients have brain and spinal chord damage. Most end up with blindness and are mentally handicapped. Cure/Treatmenr: No known cure or treatment. Blood test to see who is a carrier. b. PhenlyKetonuria (PKU) A disease where an enzyme that converts Phenylalanine to tyrosine is absent. Tyrosine is used to create melanin and some hormones. Phenylalanine is broken down abnormally (it should be converted to tyrosine) and in the process, neural damage occurs. Patients with the condition are usually babies and they end up with brain damage. Cure/Treatment: Infants are placed on a special diet to reduce intake of phenylalanine until after their nervous system is fully developed. After this, they can live normal lives. 2. Co Dominnat Inheritance A situation where if a person receives both dominant alleles for the condition from the parent, they will have the condition. People who are heterozygous will be carriers. Ex: a. Sickle Cell Anemia A disease where the blood cells of an individual become sickled or are elongated and blunt. There is a defect in the hemoglobin in these cells causing them to lose their shape. This leads to blood clots and reduced blood flow to organs. Most individuals are often tired and suffer from many diseases and often die. Cure/Treatments: None known

2 Page 2 of Autosomal Dominant Inheritance These are conditions caused by DOMINANT alleles and those having the dominant alleles are affected. Ex: a. Progeria A disease causing an individual to age rapidly. b. Huntington s A lethal disease in which the brain deteriorates over about 15 years time. 4. Incomplete Dominance Inheritance Symptoms include loss of motor coordination, memory and ability to speak. Most people die in their 40 s and 50 s. A condition where there is a blending of two traits. The Heterozygous individual will have the condition. Ex: a. HF (Familial Hypercholesterolemia) People receiving the allele for this trait will have twice the normal cholesterol levels in their blood. 5. Sex Linked Inheritance These are traits usually inherited as a recessive allele on the X chromosome. Ex: a. Red Green Colourblindness. b. Muscular Dystrophy c. Hemophilia

3 Page 3 of 10 Pedigrees and Pedigree Charts Pedigree: A chart/diagram that shows the genetic relationships among a group of related individuals. Pedigrees are like family trees Function of a Pedigree: A pedigree is used to trace the inheritance of traits in humans.

4 Page 4 of 10 Diagnosis and Treatment of Genetic Disorders Detection of Genetic Disorders Several methods are used to detecting genetic disorders. They are: 1. Amnioscentesis Fluid from amniotic sac is removed with a needle. Karyotype is prepared along with other genetic tests to determine disorders. 2. CVS (Chorionic Villus Sampling) Cells are removed from the chorion or placenta and examined for genetic disorders. 3. Fetoscopy Camera is used to view the fetus of a female to look for physical abnormalities that may suggest genetic disorders. 4. Genetic Markers These are markers (indicators) found in the DNA that indicate the inheritance of a defective gene or a gene casing a disorder. There are two types of these markers: a. Linked Markers A known sequence of nucleotides located close to a gene that causes a disorder. b. Gene Specific Marker A sequence of DNA that is part of the Gene itself. Genetic Markers are found using radioactive or fluorescent tags on complementary DNA nucleotide sequences of the suspected marker. Treatment of Genetic Disorders Several methods of treatment are available for genetic disorders. A. 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 advised of options such as special diets etc. they can place their children on. B. Surgery Surgery can repair some genetic conditions such as cleft palate

5 Page 5 of 10 C. Environmental Control This is the controlling of the environment in which an individual with a disorder lives. o Ex: People with Albinism (lack of melanin skin pigment) MUST avoid sunlight. These people usually are fully clothed all the time and only go out at night etc. D. Gene Therapy A procedure in which normal or modified genes are transferred into the defective cells of an individual. The new genes should cause the cells to work normally and fix the genetic disorder. Question? Many ethical questions arise from the use of Gene therapy. a. Are we playing God? b. Who gets the modified gene and who does not? c. For what conditions are genes produced/used? d. What cost and who pays for the procedure? Genetic Engineering Genetic Engineering: The manipulation of an organism s genetic material to modify the proteins it produces. How does genetic engineering operate? There are several steps involved in manipulating or modifying the DNA of an organism. The steps or techniques are outlined below. a. Restriction Enzymes These are enzymes such as Restriction Endonuclease used to CUT DNA into short fragments. Each fragment of DNA has Sticky Ends (short segments of unpaired nucleotides on each end of a fragment). Restriction Enzyme Original DNA Cut DNA fragment Sticky Ends

6 Page 6 of 10 b. Recombinant DNA This is a new segment of DNA made by combining or joining DNA from two different sources. DNA Fragment cut by Restriction enzymes DNA Fragment inserted into another piece of DNA making Recombinant DNA c. DNA Amplification The process of generating a large sample of DNA from a single gene or DNA fragment. Two methods are used in this process I. Cloning Vectors This is the use of a bacteria or virus to produce many copies of a foreign DNA sequence. o Foreign DNA is spliced into the DNA of either a virus or bacteria and they are then allowed to reproduce. The DNA is then harvested from the bacteria or virus at a later time. II. Polymerase Chain Reaction(PCR) An automated method of reproducing DNA by using enzymes such as DNA polymerase and primers. DNA section is placed in a solution of free nucleotides. (The free nucleotides will be used to make copies of the DNA section) Heated to open up the double helix DNA polymerase is added and DNA replication occurs. Cycle is repeated several times End result is lots of DNA sequence that was wanted.

7 Page 7 of 10 d. Gel Electrophoresis Fragments of DNA are separated according to their mass and electrical charge. o 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. o After a while a characteristic pattern of bands emerges. This is known as the DNA FINGERPRINT of a person. e. DNA Sequencing The process of reading DNA fragments so as to determine the exact sequence of base pairs in a sample of DNA. 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 if 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 I % of ALL human DNA is identical. II. There are approximately genes in the human population. Much less than the expected 100,000.

8 Page 8 of 10 Risks and Benefits of Human Genome Project Risks Privacy All of genome is known, so your DNA is now so unique anymore. Financial If genetic disorders can be determined to exist in population, can insurance etc, be denied. Ethical Should we be playing God? Benefits Knowledge of predisposition to disease We know about the predisposition to disease so treatments and/or prevetions can be implemented. Analysis of diseases Diseases that are known can be analyzed and preventions/cures created. Genetically Modified Foods and Organisms GMO = Genetically Modified Organism GMF = Genetically Modified Foods Note: Most GMF s and some GMO s are Transgenic Transgenic: Genetically engineered products approved for agricultural use in North America. Examples of GMF s/gmo s (Transgenic products) 1. Herbicide resistant corn 2. Cows with high milk production 3. Rice with greatear amounts of Vitamin A and Iron (Golden Rice) 4. Transgenic Salmon 5. Insulin producing bacteria 6. PCB eating bacteria 7. Oil eating bacteria Risks and Benefits of GMO s / GMF s 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.

9 Page 9 of 10 Cloning Cloning: The production of an organism that is genetically identical to another. Ex: Dolly the sheep Question? Answer: How is cloning accomplished? We will use sheep as our example of this process. The Cloning of a Sheep Egg Donor Unfertilized eggs are collected and nuclei removed and discarded Udder Donor Udder cells are collected and treated to prevent cell division. Nuclei are removed. Nucleus (from udder) is transplanted into empty egg cell. An electric current is applied to restart the cell cycle. Some cells divide to produce an embryo Embryo is implanted into uterus of surrogate sheet Lamb is born that is identical to the donor of the udder nuclei. Benefits and Risks of Cloning 1. Speed of Production 2. Elimination of disease 3. Manipulation of traits 4. Reducing genetic variability (all are alike) 5. Embryo use and destruction Ethics????

10 Page 10 of 10 Therapeutic Cloning.vs. Reproductive Cloning in Humans Therapeutic Cloning: The culturing of human cells for use in treating medical disorders. Ex: Using cloned Pancreatic cells to cure diseased cells of human pancreas. Reproductive Cloning: The development of a cloned embryo for the purpose of creating a cloned human being. Ex: Cloning humans