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BIOE 109 Summer 2009 Lecture 4- Part I Mutation and genetic variation

BIOE 109 Summer 2009 Lecture 4- Part I Mutation and genetic variation. Four basic processes that can explain evolutionary changes:. Mutation 2. Gene Flow 3. Genetic drift 4. Natural selection. Sources of genetic variation Crossing over during meiosis- creates new

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BIOE 109 Summer 2009 Lecture 4- Part I Mutation and genetic variation

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  1. BIOE 109 Summer 2009 Lecture 4- Part I Mutation and genetic variation

  2. Four basic processes that can explain evolutionary changes: • Mutation • 2. Gene Flow • 3. Genetic drift • 4. Natural selection

  3. Sources of genetic variation • Crossing over during meiosis- creates new • combinations of alleles on individual chromosomes • 2. Independent assortment- creates new combinations • chromosomes in the daughter cells

  4. Sources of genetic variation • Crossing over during meiosis- creates new • combinations of alleles on individual chromosomes • 2. Independent assortment- creates new combinations • chromosomes in the daughter cells • 3. Mutations- create completely new alleles and genes

  5. General classes of mutations

  6. General classes of mutations Point mutations “Copy-number” mutations Chromosomal mutations Genome mutations

  7. Point mutations

  8. Point mutations There are four categories of point mutations:

  9. Point mutations There are four categories of point mutations: 1. transitions (e.g.,A  G, C  T)

  10. Point mutations There are four categories of point mutations: 1. transitions (e.g.,A  G, C  T) 2. transversions (e.g., T  A, C  G)

  11. Point mutations There are four categories of point mutations: 1. transitions (e.g.,A  G, C  T) 2. transversions (e.g., T  A, C  G)

  12. Point mutations There are four categories of point mutations: 1. transitions (e.g., A  G, C  T) 2. transversions (e.g., T  A, C  G) 3. insertions (e.g., TTTGAC  TTTCCGAC)

  13. Point mutations There are four categories of point mutations: 1. transitions (e.g., A  G, C  T) 2. transversions (e.g., T  A, C  G) 3. insertions (e.g., TTTGAC  TTTCCGAC) 4. deletions (e.g., TTTGAC  TTTC)

  14. Point mutations There are four categories of point mutations: 1. transitions (e.g., A  G, C  T) 2. transversions (e.g., T  A, C  G) 3. insertions (e.g., TTTGAC  TTTCCGAC) 4. deletions (e.g., TTTGAC  TTTC) • in coding regions, point mutations can involve silent (synonymous) or replacement (nonsynonymous) changes.

  15. Point mutations There are four categories of point mutations: 1. transitions (e.g., A  G, C  T) 2. transversions (e.g., T  A, C  G) 3. insertions (e.g., TTTGAC  TTTCCGAC) 4. deletions (e.g., TTTGAC  TTTC) • in coding regions, point mutations can involve silent (synonymous) or replacement (nonsynonymous) changes. • in coding regions, insertions/deletions can also cause frameshift mutations.

  16. Loss of function mutations in the cystic fibrosis gene

  17. “Copy-number” mutations

  18. “Copy-number” mutations • these mutations change the numbers of genetic elements.

  19. “Copy-number” mutations • these mutations change the numbers of genetic elements. •gene duplication events create new copies of genes.

  20. “Copy-number” mutations • these mutations change the numbers of genetic elements. •gene duplication events create new copies of genes. • one important mechanism generating duplications is unequal crossing over.

  21. Unequal crossing-over can generate gene duplications

  22. Unequal crossing-over can generate gene duplications

  23. Unequal crossing-over can generate gene duplications lethal?   neutral?

  24. “Copy-number” mutations • these mutations change the numbers of genetic elements. •gene duplication events create new copies of genes. • one mechanism believed responsible is unequal crossing over. • over time, this process may lead to the development of multi-gene families.

  25.  and -globin gene families Chromosome 11 Chromosome 16

  26. Timing of expression of globin genes

  27. Retrogenes may also be created • retrogenes have identical exon structures to their “progenitors” but lack introns!

  28. Retrogenes may also be created • retrogenes have identical exon structures to their “progenitors” but lack introns! Example: jingwei in Drosophila yakuba

  29. Retrogenes may also be created • retrogenes have identical exon structures to their “progenitors” but lack introns! Example: jingwei in Drosophila yakuba  Alcohol dehydrogenase (Adh) Chromosome 2 Chromosome 3

  30. Retrogenes may also be created • retrogenes have identical exon structures to their “progenitors” but lack introns! Example: jingwei in Drosophila yakuba  mRNA  Alcohol dehydrogenase (Adh) Chromosome 2 Chromosome 3

  31. Retrogenes may also be created • retrogenes have identical exon structures to their “progenitors” but lack introns! Example: jingwei in Drosophila yakuba  mRNA  cDNA  Alcohol dehydrogenase (Adh) Chromosome 2 Chromosome 3

  32. Retrogenes may also be created • retrogenes have identical exon structures to their “progenitors” but lack introns! Example: jingwei in Drosophila yakuba  mRNA  cDNA   Alcohol dehydrogenase (Adh) “jingwei” Chromosome 2 Chromosome 3

  33. Whole-genome data yields data on gene families

  34. “Copy-number” mutations •transposable elements (TEs) are common.

  35. “Copy-number” mutations •transposable elements (TEs) are common. • three major classes of TEs are recognized:

  36. “Copy-number” mutations •transposable elements (TEs) are common. • three major classes of TEs are recognized: 1. insertion sequences (700 – 2600 bp) 

  37. “Copy-number” mutations •transposable elements (TEs) are common. • three major classes of TEs are recognized: 1. insertion sequences (700 – 2600 bp)  2. transposons (2500 – 7000 bp)

  38. “Copy-number” mutations •transposable elements (TEs) are common. • three major classes of TEs are recognized: 1. insertion sequences (700 – 2600 bp)  2. transposons (2500 – 7000 bp) 3. retroelements

  39. Chromosomal inversions lock blocks of genes together

  40. Inversions act to suppress crossing-over…  inviable  inviable

  41. Inversions act to suppress crossing-over…  inviable  inviable … and can lead to co-adapted gene complexes

  42. Chromosomal inversions in Drosophila pseudoobscura Here is a standard/arrowhead heterozygote:

  43. Here are more inversion heterzygotes:

  44. Chromosomal translocations are also common

  45. Changes in chromosome number are common

  46. Changes in chromosome number are common • in mammals, chromosome numbers range from N = 3 to N = 42.

  47. Changes in chromosome number are common • in mammals, chromosome numbers range from N = 3 to N = 42. • in insects, the range is from N = 1(some ants) to N = 220 (a butterfly)

  48. Changes in chromosome number are common • in mammals, chromosome numbers range from N = 3 to N = 42. • in insects, the range is from N = 1(some ants) to N = 220 (a butterfly) • karyotypes can evolve rapidly!

  49. Muntiacus reevesi Muntiacus muntjac

  50. Muntiacus reevesi; N = 23 Muntiacus muntjac; N = 4

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