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Pitt BIOSC 0815 - Genes and Diseases
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BIOSCI 0815 Lecture 1 Outline of Current Lecture I. Tay-Sachsa. CarriersII. TwinsIII. Chemical Reactionsa. EnzymesIV. DNAV. Genetic Disorders Current Lecture II. Tay-Sachsa. Tay-Sachs is a disease caused by the inability to process a protein that breaks down fat inthe brain, resulting in a fat build up in the brain. A usually fatal disease, it causes deaths in children typically between five and seven. To get Tay-Sachs you must inherit the disease from both parents. b. Some cultures and groups of people are more vulnerable to this disease such as Ashkenazi Jews, French Canadians, Lousisan Cajuns. One in 250 of the general population will have this disease. c. Carriers.i. Carriers are people who do not have the symptoms of the disease but can pass iton to their children. This is when the disease is only shown in the recessive gene (little “a”). The child must have two recessive genes to have the disease. ii. Parents with the genes Aa are carriers of the disease. If two carriers have a child,that child has a 1 in 4 chance of having the disease (aa). The child has a 1 in 2 chance of being a carrier and a 1 in 4 chance of being free of the disease.iii. These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.iv. If one parent is a carrier of the disease and the other does not have the recessive gene the children have a 50% chance of being carriers, and 50% chance of not being carriers. None of the children will have the disease.v.vi. Tay-Sachs causes seizures by age two, incapacitates the child by age three. Signs of the disease begin to show at six months, before which the child shows normaldevelopment.vii. The problem that causes Tay-Sachs is that the child is missing an enzyme (a chemical that helps other chemical reactions to occur. In the absence of this enzyme, reactions may not occur or may take a long time to occur.III. Twinsa. Monozygotic twins are identical twins that come from one fertilized egg and one sperm. They share a placenta in the womb.b. Dizygotic twins are fraternal twins from two fertilized eggs by two different sperm. Thereare two placentas.IV. Chemical Reactionsa. Chemical reactions are when chemicals are joined together or are broken apart. For example: A+B  AB or ABA +Bb. Enzymesi. Enzymes bring chemicals together so that reactions can occur. They are not usedup in the reaction.ii. Enzymes are a type of protein. Proteins are a versatile class of chemicals which carry out functions in the cells. They can be receptors which receive signals that tell cells what to do or they can help reactions occur.c. Polymerization: when a monomer (a single unit) is joined together to form a polymer.d. In Tay-Sachs, the enzyme that is missing is Hexosaminidase A. This enzyme is missing because the information in the DNA used to make the protein is incorrect.V. DNA (Deoxyribonucleic Acid)a. Our cells contain a code to make proteins. This is the genetic code. b. Imagine that DNA is a document on reserve in the library. If you want to read the text, you have to make a copy of it. This copy is called RNA. The process of making the copy iscalled transcription. The RNA is able to leave the nucleus of a cell. It is then translated to make proteins (enzymes). Once it is no longer needed the RNA copy degenerates outsideof the nucleus and is destroyed. VI. Genetic Disordersa. Genetic disorders are when something is wrong with the instructions in the DNA of how to make a protein.b. Often a mutation alters the information in the genetic code. IN genetic diseases the genetic code is mutated which means that the information for a protein is changed from normal.c. What causes genetic disorders?i. Often the causes of the mutations that result in genetic disorders are unknown. ii. Sometime they are induced by1. UV radiation2. Toxic chemicals3. Alcohol, drugs, tobaccoiii. The above contribute to a higher incidence of mutation.d. What can we do to prevent genetic disorders?i. Genetic counselingii. Understanding the human genome (scientists are studying this now, trying to see if cures can be made for many diseases by changing the genome)iii. Replacement drugs: sometimes the protein can be supplemented by medicinesiv. Special diets: if someone is unable to process a certain food because of a geneticdisease a special diet would help them avoid that food.VII. Gene therapy (the idea that we could replace a bad copy of a gene with a good one. This idea is still being


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Pitt BIOSC 0815 - Genes and Diseases

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