Chapter 22 Lecture Outline: Mutations and Genetic Disease PDF

Chapter 22 Lecture Outline Prepared by Andrea D. Leonard University of Louisiana at Lafayette Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.  Mutations and Genetic Disease A mutation is a change in the nucleotide sequence...

Chapter 22 Lecture Outline Prepared by Andrea D. Leonard University of Louisiana at Lafayette Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.  Mutations and Genetic Disease A mutation is a change in the nucleotide sequence in a molecule of DNA. Some mutations are random, while others are caused by mutagens. A point mutation is the substitution of one nucleotide for another. 2  Mutations and Genetic Disease A deletion mutation occurs when one or more nucleotides is/are lost from a DNA molecule. An insertion mutation occurs when one or more nucleotides is/are added to a DNA molecule. 3  Mutations and Genetic Disease A silent mutation has a negligible effect to the organism, because the resulting amino acid is identical. The mutation has no effect. 4  Mutations and Genetic Disease A mutation that produces a protein with one different amino acid usually has a small to moderate effect on the protein overall. Some proteins, such as hemoglobin, substitution of just one amino acid can result in the fatal disease sickle cell anemia. 5  Mutations and Genetic Disease If a mutation causes a big change, like producing a stop codon, the remainder of the protein will not be synthesized, which can have catastrophic results. 6  Mutations and Genetic Disease When a mutation causes a protein deficiency or defective protein synthesis and this mutation is passed through generations, it is a genetic disease. Cystic fibrosis results from defective cyctic fibrosis transmembrane conductance regulator (CFTR); the effects are extremely thick lung mucus and low pancreatic secretions. Galactosemia results from a deficiency of an enzyme needed for galactose metabolism and can cause mental retardation. 7 Table 22.5  Recombinant DNA General Principles Recombinant DNA is synthetic DNA that contains segments from more than one source. Three key elements are needed to form recombinant DNA: 1. A DNA molecule into which a new DNA segment will be inserted. 2. An enzyme that cleaves DNA at specific locations. 2. A gene from a second organism that will be inserted into the original DNA molecule. 9 Recombinant DNA General Principles First, bacterial plasmid DNA is cut by the restriction endonuclease EcoRI, which cuts in a specific place. This gives a double strand of linear plasmid DNA with two ends ready to bond, called sticky ends. 10  Recombinant DNA General Principles Then, a second sample of human DNA is cut with the same EcoRI. This forms human DNA segments with sticky ends that are complimentary to the plasmid DNA. 11  Recombinant DNA General Principles Combining the two pieces of DNA (with DNA ligase enzyme) forms DNA containing the new segment. This DNA chain is slightly larger because of its additional segment. 12  Recombinant DNA Polymerase Chain Reaction Polymerase chain reaction (PCR) amplifies a specific portion of a DNA molecule, producing millions of exact copies. 13  Recombinant DNA Polymerase Chain Reaction Four elements are needed to amplify DNA by PCR: 1. The segment of DNA that must be copied. 2. Two primers—short polynucleotides that are complementary to the two ends of the segment to be amplified. 3. A DNA polymerase enzyme to catalyze the synthesis of a complementary strand. 4. Nucleoside triphosphates—the source of the A, T, C, and G needed to make the new DNA. 14  Recombinant DNA HOW TO Use the Polymerase Chain Reaction to Amplify a Sample of DNA Heat the DNA segment to unwind the Step double helix to form single strands. 15  Recombinant DNA HOW TO Use the Polymerase Chain Reaction to Amplify a Sample of DNA Add primers that are complementary to Step the DNA sequence at either end of the DNA segment. 16  Recombinant DNA HOW TO Use the Polymerase Chain Reaction to Amplify a Sample of DNA Step 17  Recombinant DNA HOW TO Use the Polymerase Chain Reaction to Amplify a Sample of DNA Use a DNA polymerase and added Step nucleotides to lengthen the DNA segment. After each cycle the amount of DNA is doubled, so after 20 cycles, 1,000,000 copies have been made. 18  Focus on the Human Body DNA Fingerprinting The DNA of each individual person is unique, so DNA can be used as a method of identification. Any type of cell (skin, saliva, semen, blood, etc.) can be used to obtain a DNA fingerprint. The DNA is first amplified by PCR, and then cut by restriction enzymes. The DNA fragments are then separated by size by gel electrophoresis. 19  Focus on the Human Body DNA Fingerprinting DNA fragments can be visualized on X-ray film after they have been separated: 20  Focus on Health & Medicine Viruses A virus is an infectious agent consisting of a DNA or RNA molecule that is contained within a protein coating. It is incapable of replicating alone, so it invades a host organism and makes the host replicate the virus. Many prevalent diseases like the common cold, influenza, and herpes are viral in origin. A vaccine is an inactive form of a virus that causes a person’s immune system to produce antibodies to the virus to ward off infection. 21  Focus on Health & Medicine Viruses A virus with an RNA core is called a retrovirus. 22  Focus on Health & Medicine Viruses Retroviruses invade a host and then synthesize viral DNA by reverse transcription. The viral DNA can then transcribe RNA, which then directs protein synthesis (new retroviral particles to infect other cells). Acquired immune deficiency syndrome (AIDS) is caused by the retrovirus human immunodeficiency virus (HIV). 23 Focus on Health & Medicine Viruses 24