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MUTATIONS

MUTATIONS. Definition of mutation Changes in the genetic material. Mutations are not always a bad thing. Gene Mutations. Chromosome. Gene. Remember Translation?. What is this? What does it tell us? What Amino Acid does the codon GCA code for? What about CGU?.

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MUTATIONS

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  1. MUTATIONS

  2. Definition of mutation Changes in the genetic material. Mutations are not always a bad thing.

  3. Gene Mutations Chromosome Gene

  4. Remember Translation? What is this? What does it tell us? What Amino Acid does the codon GCA code for? What about CGU?

  5. 11.3 Section Summary 6.3 – pages 296 - 301 Mutations • Organisms have evolved many ways to protect their DNA from changes. • In spite of these mechanisms, however, changes in the DNA occasionally do occur. • Any change in DNA sequence is called a mutation. • Mutations can be caused by errors in replication, transcription, cell division, or by external agents.

  6. 11.3 Section Summary 6.3 – pages 296 - 301 Mutations in reproductive cells • Mutations can affect the reproductive cells of an organism by changing the sequence of nucleotides within a gene in a sperm or an egg cell. • If this cell takes part in fertilization, the altered gene would become part of the genetic makeup of the offspring.

  7. Two major types of mutations: A. Gene mutation • Point mutation 1. Substitution • Frameshift mutation • Insertion • Deletion B. Chromosomal mutation • Deletion • Duplication • Inversion • Translocation

  8. Gene Mutations: • Pointmutation - changes involving one or a few (2-3) nucleotides. Example - Substitution

  9. Point Mutations: • Substitution Oringinal Strand - GCA Mutated Strand - GTA Effects only one Amino Acid in the sequence.

  10. Gene Mutations: Frameshiftmutations a shift in the “reading frame” of the genetic message. Or – changes the whole sequence.

  11. Frameshift Mutations: • Insertion – Inserting an additional base into the genetic sequence. 2. Deletion - Deleting a base from the genetic sequence. • The cow jumped over the moon.becomes • The coj umpedo vert hem oon.

  12. INSERTIONOriginal Strand - TACGCATGGAAT Mutated Strand - TATCGCATGGAAT Changes the entire message. It is no longer the same sequence – so it is no longer making the same protein.

  13. DELETIONOringinal Strand - TACGCATGGAAT Mutated Strand - ACGCATGGAAT Again, it changes the entire message. It is no longer the same sequence – so it is no longer making the same protein.

  14. Chromosomal Mutations Chromosome Gene

  15. Chromosomal Mutations changes in the structure of a chromosome. • Deletion – deleting part of the chromosome • Duplication – duplicating part of the chromosome • Inversion – inverting two sections of a chromosome - Translocation: when a section of each chromatid trade places.

  16. Chromosomal Mutations Deletion: deleting part of the chromosome So, what is actually being deleted?

  17. Chromosomal Mutations Duplication: duplicating part of the chromosome So, what is actually being duplicated?

  18. Chromosomal Mutations Inversion: inverting two sections of a chromosome

  19. Chromosomal Mutations Translocation: when a section of each chromatid trade places.

  20. 11.3 Section Summary 6.3 – pages 296 - 301 Causes of Mutations • Any agent that can cause a change in DNA is called a mutagen. • Mutagens include radiation, chemicals, and even high temperatures. • Forms of radiation, such as X rays, cosmic rays, ultraviolet light, and nuclear radiation, are dangerous mutagens because the energy they contain can damage or break apart DNA.

  21. 11.3 Section Summary 6.3 – pages 296 - 301 Causes of Mutations • The breaking and reforming of a double-stranded DNA molecule can result in deletions. • Chemical mutagens include dioxins, asbestos, benzene, and formaldehyde, substances that are commonly found in buildings and in the environment. • Chemical mutagens usually cause substitution mutations.

  22. Repairing DNA • Repair mechanisms that fix mutations in cells have evolved. • Enzymes proofread the DNA and replace incorrect nucleotides with correct nucleotides. • These repair mechanisms work extremely well, but they are not perfect. • The greater the exposure to a mutagen such as UV light, the more likely is the chance that a mistake will not be corrected.

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