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Two loci

Two loci. long chrom. long chrom. short chrom. short chrom. Parent A. AA/AA x BB/BB. Parent B. A. A. B. B. A. A. B. B. locus 2. locus 2. locus 1. locus 1. AB/AB. (F1). Locus1/Locus 2. AB/AB x AB/AB. 16 possibilities. (F2). Two loci, incomplete dominance (new and improved).

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Two loci

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  1. Two loci long chrom long chrom short chrom short chrom Parent A AA/AA x BB/BB Parent B A A B B A A B B locus 2 locus 2 locus 1 locus 1 AB/AB (F1) Locus1/Locus 2 AB/AB x AB/AB 16 possibilities (F2)

  2. Two loci, incomplete dominance(new and improved)

  3. 2-locus interaction For example: locus 2 is polymorphism in a transcription factor gene that affects protein binding affinity, locus 1 is in a binding site Effect of J at locus 2 Effect of variation at locus 2 depends on genotype at locus 1: non-additive

  4. NO progeny as extreme as diploid hybrid

  5. NO progeny as extreme as diploid hybrid Diploid hybrid Lab parent Pathogenic parent

  6. Tested in hybrid diploids Pathogenic Pathogenic Lab Lab Different in sequence

  7. One mutant gene… From pathogenic strain

  8. One mutant gene… From pathogenic strain From lab strain

  9. Two mutant genes… From pathogenic strain From lab strain

  10. Two mutant genes… From pathogenic strain From lab strain

  11. Two mutant genes… From pathogenic strain Again, diploid with this gene from the pathogenic strain grows BETTER at high T. From lab strain

  12. Three mutant genes From lab strain Diploid with this gene from the pathogenic strain grows WORSE at high T! From pathogenic strain

  13. Three mutant genes From pathogenic strain From pathogenic strain From pathogenic strain

  14. Three mutant genes From pathogenic strain From pathogenic strain From pathogenic strain

  15. Three mutant genes From pathogenic strain From pathogenic strain From pathogenic strain Alleles from the same strain at different genes/loci can have different effects.

  16. Three mutant genes in same “locus”

  17. Three mutant genes in same “locus”

  18. Three mutant genes So why did 0/900 haploid progeny have a phenotype as extreme as the diploid hybrid?

  19. NO progeny as extreme as diploid hybrid Diploid hybrid Lab parent Pathogenic parent

  20. NO progeny as extreme as diploid hybrid Diploid hybrid Lab parent Pathogenic parent

  21. Linked mutations of opposite effect Path

  22. Linked mutations of opposite effect Path Lab

  23. Linked mutations of opposite effect Path Lab Very unlikely

  24. “Multiple linked loci”

  25. Model organism to human

  26. Why pigmentation? • Camouflage • Sexual selection • Protection from UV • Controlling light scatter • (Sunlight for vitamin D) • Accident—something else selected for nearby

  27. Golden mutation

  28. Golden mutation Melanosomes, melanin-producing organelles

  29. Golden mutation 1981: original mutant arose spontaneously in the lab. Showed mendelian segregation (1 locus), and is recessive.

  30. Golden mutation 1981: original mutant arose spontaneously in the lab. Showed mendelian segregation (1 locus), and is recessive. Dramatic, single-locus differences not common in the wild. Why not?

  31. Linkage analysis with sparse markers mapped golden to markers on chromosome 18, but high-resolution position of markers unknown.

  32. Linkage analysis with sparse markers mapped golden to markers on chromosome 18, but high-resolution position of markers unknown. Genome sequence not completed…

  33. Linkage analysis with sparse markers mapped golden to markers on chromosome 18, but high-resolution position of markers unknown. Genome sequence not completed… Hybrid cell lines not available…

  34. Library screen Shear, ligate Native WT chromosomes

  35. Library screen Shear, ligate Native WT chromosomes Genomic library

  36. Library screen Shear, ligate Native WT chromosomes Genomic library Hybridize to marker oligo 85 kb DNA containing chr 18 marker

  37. Fine-mapping 85 kb Inject into golden larvae

  38. Fine-mapping 85 kb Inject into golden larvae

  39. Fine-mapping Golden uninjected 85 kb Inject into golden larvae

  40. Fine-mapping WT uninjected Golden uninjected 85 kb Inject into golden larvae

  41. Fine-mapping WT uninjected Golden uninjected 85 kb “mosaic rescue” Inject into golden larvae

  42. Fine-mapping 85 kb

  43. Fine-mapping 85 kb slc24a5 mRNA

  44. Fine-mapping 85 kb slc24a5 mRNA Inject into golden larvae

  45. Fine-mapping WT uninjected Golden uninjected Inject into golden larvae

  46. Gene is strongly conserved Looks like a Na/Ca exchange pump

  47. Gene is strongly conserved Looks like a Na/Ca exchange pump *

  48. Gene is strongly conserved Looks like a Na/Ca exchange pump * * = premature stop codon in DNA of golden embryos

  49. Gene is strongly conserved Looks like a Na/Ca exchange pump * * = premature stop codon in DNA of golden embryos (Don’t usually see such dramatic mutations in the wild)

  50. Human can rescue fish! Human mRNA injected

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