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Understanding Genetic Mutations: Causes and Impacts

Learn about genetic mutations, including point and frameshift mutations, chromosomal mutations, and their effects. Discover causes like radiation and chemicals and the importance of DNA repair mechanisms. Get ready for your homework on DNA/RNA mutations!

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Understanding Genetic Mutations: Causes and Impacts

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  1. Put your HW in the HW folder. • What do all of the following have in common?

  2. Genetic Changes Chapter 11.3

  3. MUTATION • defined as a change in the DNA sequence • can be caused by errors in replication, transcription, cell division, or by external agents

  4. Mutations • Reproductive cells • Will be passed down to offspring • Embryo may not survive • Offspring might be sterile • Body cells • Impair cell function • Cancer • Premature aging

  5. Point Mutation: Single base alteration What do you see happening?

  6. Sickle cell anemia

  7. Frameshift Mutation A type of point mutation: single base is added or deleted from DNA How is this different than a point mutation? How is it similar?

  8. Frameshift cont’d • If groups of 3 (or multiples of 3) bases is added or deleted, it will only affect a few amino acids (1 per codon) • If 1, 2, 4 (any non-multiple of 3) is deleted, ALL amino acids will be different from the mutation onward. • Causes a change in the reading frame

  9. Cystic fibrosis – affects the lungs, liver, pancreas, small intestine, reproductive organs, and the skin

  10. Chromosomal mutations • When there are changes in the chromosome, it is considered a chromosomal mutation. • Part of a chromosome is broken off and lost • There are 4 kinds of chromosomal mutations: • Deletions, Insertions, Inversions, Translocations • Break and rejoin incorrectly • Nondisjunction

  11. Deletion: Section is lost from a chromosome

  12. Insertion: Section of 1 chromosome is added to another

  13. Inversion: segment of chromosome reverses itself

  14. For each #, what is different between the chromosome on the left to the one on the right?

  15. Translocation: Sections of 2 different chromosomes are swapped

  16. Nondisjunction Results in a change in the chromosome # in the daughter cells Polyploidy

  17. Polyploidy in strawberries Wild type Commercially propagated varieties Each cell is 1n Each cell is 8n  8 copies of each chromosome!

  18. Polyploidy in Dianthus

  19. More examples: • Consider a normal chromosome with genes in alphabetical order: a b c d e f g h i 1. Deletion: part of the chromosome has been removed: a b c g h i 2. Dupliction(Insertion): part of the chromosome is duplicated: a b c d e f d e f g h i 3. Inversion: part of the chromosome has been re-inserted in reverse order: a b c f e d g h i

  20. More examples cont. 4. translocation: parts of two non-homologous chromosomes are joined: If one normal chromosome is a b c d e f g h i and the other chromosome is u v w x y z, then a translocation between them would be a b c d e f x y z and u v w g h i.

  21. Causes of Mutations • random, mistake in base pairing • mutagens (ex. radiation, chemicals, high temperature)

  22. Radiation • contains energy that can damage or break apart DNA • breaking and reforming of DNA can result in deletions • may convert one base into another or fuse two bases together

  23. Chemical mutagens • include asbestos, benzene, and formaldehyde • usually cause substitution mutations

  24. Sources of formaldehyde

  25. DNA repair • “Proofreading” is performed by enzymes like DNA ligase. • Such repair mechanisms work very efficiently, although they are not perfect. • Thus, it is still best to avoid situations that would expose us to mutagens.

  26. HW for 3/13 • Due tomorrow: • Worksheet on DNA/RNA and mutations • Field trip permission slip and $5 • Due Friday: Ch.12 Index Cards

  27. Problem-Solving Lab 11-3 (p. 299) • In your groups, answer questions 1-4 on a blank sheet of paper with everyone’s name on it. • Group with the most correct answers gets 2 bonus points for the day. • You have 7 min – starting now!

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