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DNA, Mutations & Genetic Screening

DNA, Mutations & Genetic Screening. Genes  Protein. Genes are determined by the order of the nucleic acids (A, T, G, C) These are the instructions that tell a cell which proteins to make Example Sequence: A T G C A A T C G T C A G T T. Mutation.

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DNA, Mutations & Genetic Screening

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  1. DNA, Mutations & Genetic Screening

  2. Genes  Protein • Genes are determined by the order of the nucleic acids (A, T, G, C) • These are the instructions that tell a cell which proteins to make • Example Sequence: A T G C A A T C G T C A G T T

  3. Mutation • A change in the order of the nucleic acids

  4. Examples of Mutations • Example Sequence: A T G C A A T C G T C A G T T • Mutated Sequences: A T C A A T C G T C A G T T(G is deleted) A T G C A A T A C G T C A G T T (A is added)

  5. Example: Sickle Cell Anemia • Abnormally shaped red blood cells • Different type of hemoglobin • Less oxygen can be delivered throughout body • Inheritable disease

  6. What causes mutations? Mutagens • Chemical: • Mercury in cigarettes • Nitrous acid – produced when preservatives (nitrates) are broken down in the body • Radiation: • X-rays • UV light

  7. Mutations can be: • Harmful – the wrong protein is made and the cell cannot function normally Ex: sickle cell anemia • Beneficial – the outcome benefits the organism Ex: antibiotic resistance in bacteria • Neutral – no change (same protein is made or mutation effects an area of DNA that does not contain genes)

  8. Can we correct mutations? • Not yet • Lots of research is going into gene therapy, but not much success has been seen in clinical trials

  9. DNA Screening • Phenylketonuria (PKU) – an inheritable condition in which the baby cannot produce the enzyme required to break down phenylalanine • Build-up of phenylalanine is harmful to the nervous system and can lead to brain damage • Why test for this? Mother can prevent problems in her child by following a strict low-phenylalanine diet

  10. Down Syndrome • A genetic condition in which a person has 47 chromosomes instead of the usual 46. • Extra copy of chromosome 21 • Common physical signs include: • Decreased muscle tone at birth • Flattened nose • Upward slanting eyes • Wide, short hands with short fingers

  11. Huntington’s Disease • A disorder passed down through families in which certain nerve cells in the brain waste away, or degenerate. • Caused by a genetic defect on chromosome #4 • CAG repeat • If one of your parents has Huntington's disease, you have a 50% chance of getting the gene for the disease. If you get the gene from your parents, you will develop the disease at some point in your life, and can pass it onto your children.

  12. DNA Screening • Symptoms • Behaviour changes (antisocial, restlessness, hallucinations) • Abnormal and unusual movements • Dementia that slowly gets worse • Anxiety, stress, tension • Difficulty swallowing

  13. Huntington’s Disease

  14. Should individuals get tested? • Would you want to know if you were going to get Huntington’s disease sometime in your life even though there is no cure? • Would it change your life decisions? (i.e. Having children)

  15. Ethical Issues and Drug Research • Cost • Time • Testing – animals/humans?

  16. Altering Genes • Species whose genes are altered are often called genetically modified organisms (GMOs) or transgenic organisms • Examples: • E. Coli bacteria have been altered to produce insulin • Crops can be modified to resist pests, have a higher nutritional value, etc.

  17. Corn • Scientists have genetically modified sweet corn so that it produces a poison which kills harmful insects • Called Bt-corn, because the insect-killing gene in the plant comes from the bacteria Bacillus thuringiensis.

  18. Cloning • The process of creating identical genetic copies of an organism • Genes, cells, or entire organism • Used when you take a ‘cutting’ of a plant

  19. Cloning of Dolly – Video Clip • 1996 - first mammal created from a cell of an adult sheep • Died at the age of 6 • http://www.youtube.com/watch?v=txr8-0RaD-A

  20. Homework Tonight • P. 22 #7, 8 • P. 26 #12 • P. 28 #5, 6, 8

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