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MUTATIONS

MUTATIONS. MUTATIONS. The alteration of an organism’s DNA Wide range of mutations Most mutations are automatically repaired by the organism’s enzymes… …therefore they have no effect. MUTATIONS. However…when the mutation is NOT repaired…

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MUTATIONS

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  1. MUTATIONS

  2. MUTATIONS • The alteration of an organism’s DNA • Wide range of mutations • Most mutations are automatically repaired by the organism’s enzymes… • …therefore they have no effect.

  3. MUTATIONS • However…when the mutation is NOT repaired… • The resulting altered chromosome/gene structure is passed to ALL subsequent daughter cells of the mutant cell… • Mutations can be good or bad.

  4. When are mutations inherited? • Mutations that occur in regular body cells (somaticcells) will affect all daughter cells, but will not be passed to offspring • Can contribute to aging process • May lead to cancer…

  5. When are mutations inherited? For example: • Mutation in lung cell will lead to cancer, but cancer isn’t passed on to offspring

  6. When are mutations inherited? • Mutations will only be passed on to offspring if they occur in the gamete (sex cells) • Results in genetic disorders

  7. When are mutations inherited? • Lethalmutations result in the death of the organism • Often miscarriage

  8. What causes mutations? • Malfunction during the process of meiosis • Exposure to a physical or chemical agent • Called a mutagen • Examples: x-rays, chemicals (asbestos, formaldahyde), UV rays,

  9. Two Types 1. GENE MUTATIONS— • changes in a single gene (a segment of DNA) 2. CHROMOSOMAL MUTATIONS— • changes in whole chromosomes (chromosome number or chromosome itself)

  10. 1. GENE MUTATIONS a. POINT MUTATION (Substitution) • Single nucleotide is substituted for the wrong one • Ex: A-G instead of A-T • This can lead to…

  11. 1. GENE MUTATIONS 1) Silent mutation: has NO effect since some amino acids have multiple sequences Ex: CUC codes for leucine CUA also codes for leucine

  12. 1. GENE MUTATIONS 2) Missense mutation: causes the wrong amino acid to be in sequence Ex: CUU codes for leucine CCU codes for proline

  13. 1. GENE MUTATIONS 3) Nonsense mutation: causes an early STOP codon Ex: UCA codes for serine UGA codes for STOP

  14. THE FAT CAT ATE THE RAT THE FAT CAT ATE THE HAT POINT MUTATION—SUBSTITUTION

  15. 1. GENE MUTATIONS b. FRAMESHIFT MUTATION • insertion or deletion of one or more nucleotides • All codons are shifted • May cause serious effects • Such mutations can alter a protein so that it is unable to perform its normal functions.

  16. THE FAT CAT ATE THE RAT THE FAT CAT ATE THE RAT X TEF ATC ATA TET HER AT FRAMESHIFT MUTATION— DELETION

  17. THE FAT CAT ATE THE RAT THE FAT CAT ATE THE RAT THE FLA TCA TAT ETH ERA T FRAMESHIFT MUTATION— INSERTION

  18. Disorders caused by GENE MUTATIONS • Sickle-cell disease • Tay-Sachs disease • Huntington’s disease • Cystic Fibrosis • Albinism

  19. 2. CHROMOSOMAL MUTATIONS a. DELETION • Involves loss of a part or whole chromosome

  20. A A B C D D E E F F C DELETION

  21. 2. CHROMOSOMAL MUTATIONS b. DUPLICATION • Opposite of deletion • A segment of the chromosome is repeated

  22. A A B B C C D D E E F F B DUPLICATION

  23. 2. CHROMOSOMAL MUTATIONS c. INVERSION • Direction of genes is reversed within chromosome (part is upside-down)

  24. A B C D E F A E D INVERSION C B F

  25. 2. CHROMOSOMAL MUTATIONS d. TRANSLOCATION • When part of a chromosome breaks off and relocates to another part (non-homologous)

  26. G A A G B H B H C C I I TRANSLOCATION D J J D K E K E F L L F

  27. 2. CHROMOSOMAL MUTATIONS e. NONDISJUNCTION • Results in too few or too many chromosomes in a cell…

  28. NONDISJUNCTION • MONOSOMY • Having only ONE copy of a chromosome instead of TWO • EX: Turner’s syndrome (has only one X chromosome)

  29. NONDISJUNCTION • TRISOMY • Having THREE copies of a chromosome instead of TWO • EX: Down Syndrome (3 copies of chromosome #21, trisomy 21)

  30. NONDISJUNCTION

  31. Disorders caused by CHROMOSOMAL MUTATIONS • NONDISJUNCTION of Sex Chromosomes: • Klinefelter’s syndrome (male) • Turner’s syndrome (female) • NONDISJUNCTION of Autosomal Chromosomes: • Down Syndrome (Trisomy 21)

  32. Where can mutations occur? Somatic Cells (Body Cells) Germ Cells (Sex Cells)

  33. Somatic Cells (Body Cells) • During or before mitosis • All new cells will also be altered • The change is permanent • Only effects organism, not offspring

  34. Germ Cells (Sex Cells) • Changes can occur in egg/sperm before, during or after meiosis • Altered egg/sperm may be fertilized—passing change to offspring • Changes may or may not be harmful • Harmful changes cause birth defects

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