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Chapter 10

Chapter 10. Gene Mutation. Effects of Mutations. Prevents a protein from forming Lowers amount of a protein Alters a protein Changes the function of a protein. Lack of dystrophin causes muscle cells to weaken. Blood clots very slowly due to too little clotting factor

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Chapter 10

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  1. Chapter 10 Gene Mutation

  2. Effects of Mutations • Prevents a protein from forming • Lowers amount of a protein • Alters a protein • Changes the function of a protein Lack of dystrophin causes muscle cells to weaken. Blood clots very slowly due to too little clotting factor Skin blisters form because A.A substitution prevents layers of skin to connect Extra bases in Huntington gene adds amino acids, altering function to cause brain degneration

  3. Germline Mutation – mutation that affects all cells because the mutation occurred prior to meiosis. • Somatic mutation – change happens prior to DNA replication of mitotic division.

  4. 10.2 Causes of Mutation • Mutagen – An agent that causes a mutation Spontaneous Mutation - Tautomers – Different forms of the same nitrogen base. (Stable vs. Unstable)

  5. Spontaneous Mutation Rate • Highest mutation rate • Neurofibromatosis Type 1 (Large Gene – Dominant inheritance) • Mitochondrial Genes • Lower mutation Rates • Recessive traits? • Human genes vs. Bacterial Genes

  6. Mutational Hot Spots

  7. Mutational Hot Spots • Hot Spots – Areas on a gene that mutate often. • Repeat sequences – Replication enzymes might be “confused” • Example • Alkaptonuria • 35% of the errors occur near CCC repeats • CCC repeats only account for 9% of the gene

  8. Mutational Hot Spots • Other stretches of alternating repeats.. • Example ATATATATATATATAT • Hint: (Think of rho independent transcription.) • Palindrome Sequences (not be confused with an inverted repeat!!) • GAATTC (How is this a Palindrome?) • CTTAAG

  9. Mutational Hot Spots • Repeat patterns have issues with meiosis • Synapsis issue causes crossing over problems causes gametes with insertion or deletion issues.

  10. Induced Mutations • Purpose – We don’t know the function of the gene until it doesn’t work. Intentional Use of Mutagens Alkylating Agents (chemical) – remove a DNA base and another can be added Acridines (dye) – base is removed but not replaced causing a frameshift mutation Scientist cannot really choose where the mutation will take place with these processes

  11. Site Directed Mutagenesis • PCR • Altered Primer can target the specific sequence.

  12. Accidental Mutagens • Chernobyl • Soviet Union 1986 • 28 people died due to radiation exposure • Thyroid Rate in children of Chernobyl has increased ten-fold. • Ionizing Radation • Alpha (Least energetic..absorbed by the skin) • Uranium and Radium • Beta (Penetrate further than alpha) • H-3, C-14 • Gamma (Penetrate all the way through the body..most damaging) • Plutonium and Cesium…used in weapons& to destroy cancer cells

  13. 10.3 Types of Mutations • Missense • Nonsense • Frameshift • Deletion • Insertion • Duplication • Expanding Mutations

  14. Psuedogenes: A key to our past… • http://www.dnatube.com/video/5566/All-About-Pseudogenes

  15. Genes can move?!?! • http://highered.mcgraw-hill.com/sites/0072556781/student_view0/chapter13/animation_quiz_5.html • Transposons = “jumping genes”

  16. Expanding Genes • P generation F1 F2 (Bad) (Worse) (Worst) Repeating sequences will increase in number from one generation to another

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