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Biology 2250 Principles of Genetics

Biology 2250 Principles of Genetics. Announcements Lab 4 Information: B2250 (Innes) webpage download and print before lab. Virtual fly: log in and practice http://biologylab.awlonline.com/. B2250 Readings and Problems. Ch. 4 p. 100 – 112 Prob: 10, 11, 12, 18, 19

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Biology 2250 Principles of Genetics

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  1. Biology 2250Principles of Genetics Announcements Lab 4 Information: B2250 (Innes) webpage download and print before lab. Virtual fly: log in and practice http://biologylab.awlonline.com/

  2. B2250Readings and Problems Ch. 4 p. 100 – 112 Prob: 10, 11, 12, 18, 19 Ch. 5 p. 118 – 129 Prob: 1 – 3, 5, 6, 7, 8, 9 Ch. 6 p. 148 – 165 Prob: 1, 2, 3, 10 Ch. 7 p. 188 – 191 (Bacterial conjugation)

  3. Weekly Online Quizzes Marks Oct. 14 - Oct. 25 Example Quiz 2** for logging in Oct. 21- Oct. 25 Quiz 1 2 Oct. 28 – Oct. 31 Quiz 2 2 Nov. 4 – Nov. 7 Quiz 3 2 Nov. 10 Quiz 4 2 (Midterm 2 Thursday Nov. 17)

  4. Questions for practice 1. Gene A and gene B are linked. A test cross produces 10 AaBb progeny out of a total of 100. The estimated map distance between gene A and B is: a. 10 b. 20 c. 30 d. 40 e. 50 2. For the pedigree, indicate the most probably mode of inheritance for the rare trait. 3. For the pedigree, what is the probability that the indicated female will produce an affected child?

  5. Example Test Cross AaBb X aabb ab Exp. Obs. AB AaBb 25 10 R Ab Aabb 25 40 P aB aaBb 25 40 P ab aabb 25 10 R 100 100 How to distinguish: Parental high freq. Recombinant low freq.

  6. Quiz – 2 answers http://webct.mun.ca:8900/

  7. Mendelian Genetics    Topics: -Transmission of DNA during cell division Mitosis and Meiosis - Segregation - Sex linkage (problem: how to get a white-eyed female) - Inheritance and probability - Independent Assortment - Mendelian genetics in humans - Linkage - Gene mapping   • Gene mapping in other organisms • (fungi, bacteria) • - Extensions to Mendelian Genetics • - Gene mutation • - Chromosome mutation • - Quantitative and population genetics   

  8. Linkage Maps Useful: - studying recombination (variation) - study the structure of the genome - study gene interaction (cis, trans) - diagnosis (marker gene linked to disease gene) - constructing particular genetic combinations

  9. Linkage Maps Mapping two genes: Test cross: AaBb x aabb % RF = map distance 3 point test cross: - multiple crossovers undetected - underestimate true map distance

  10. Gene Mapping Requirements: 1. Genetic material from two different individuals 2. Recombination Examples: fungi bacteria

  11. Fungal Genetics Fungi: important organisms in the ecosystem - decomposers - pathogens important for humans - food - pathogens (Biology 4040 – Mycology)

  12. Fun Facts About Fungi http://www.herbarium.usu.edu/fungi/funfacts/factindx.htm

  13. Fungi

  14. Neurospora crassa(bread mold) Morphological mutants Biochemical mutants (one gene, one enzyme)

  15. Linkage Map Neurospora crassa Linkage group I

  16. Fungus Life Cycle vegetative stage haploid +, - mating types brief diploid stage  meiosis n n + spores + meiosis - 2n n - n

  17. Independent Assortment Diploids Test Cross AaBb X aabb gametes ab 1/4 AB AaBb 1/4 Ab Aabb 1/4 aB aaBb 1/4 ab aabb 4 phenotypes 4 genotypes

  18. Gamete Pool Gametes: Products of many meioses all pooled together A B a b AB AB ab ab AB ab P A B ab ab AB ab Ab AB Gamete P a b AB aB ab ab AB AB pool R a B ab AB AB ab R A b

  19. Tetrad Analysis Some Fungi and algae: 4 products of a single meiosis can be recovered Advantages: 1. haploid organism - no dominance 2. examine a single meiosis - test cross not needed 3. small, easy to culture 4. Tetrad Analysis - map gene to centromere

  20. Ascus with ascospores

  21. Tetrad Analysis * Types of Tetrads: 1. Unordered - 4 products mixed together 2. Ordered (linear) - 4 products lined up, each haploid nucleus can be traced back through meiosis 3. Octads - mitotic division after meiosis 8 products (2 x 4)

  22. Linear Tetrad Analysis + = a+ a a a a + a + Life Cycle: + Meiosis + Diploid Haploid + Mating: a x +  a /+ n n 2n 4 haploid products

  23. Linear Tetrad Analysis a mitosis a a a a + a + + + + + 4 haploid products 8 haploid spores (Octad)

  24. Linear Tetrad Analysis Two types of asci: 1. no crossover----> first division segregation (MI) 2. crossover between gene and centromere-----> second division segregation (MII)

  25. Mapping gene to centromere First Division a a a a a a + + + + No Crossover + +

  26. First division segregation meiosis A A A A a a a a

  27. Mapping gene to centromere Second division a a a + a + + a + a + + crossover

  28. Second division segregation A A a** a** A** A** a a ** recombinant

  29. 1st and 2nd Division segregation First Division Second division a a a a a a a + a a a + + + + + a + + a No Crossover + + + + Crossover

  30. Mapping gene to centromere MI = 86 MII = 14 a + a + + a a + a + + a a + + a a + a + + a a + + a a + a + + a a + a + + a + a + a + a + a + a 43 43 3 4 3 4 Total = 100 I II

  31. Mapping gene to centromere MI = 86 MII = 14 14/100 = 14 % of meioses showed a crossover ½ of the crossover products recombinant RF = ½ x 14 % = 7 % a 7 m.u.

  32. Tetrad Analysis Tetrads: Ordered (linear): map gene to centromere

  33. Sex in Bacteria E. coli

  34. Haploid

  35. conjugation

  36. Origin of Plasmid genes from Lactococcus lactis Bacteria used to make cheese and yogurt Plasmids: location of antibiotic resistant genes

  37. Recombination in Bacteria and viruses Human Health: - antibiotic resistance - new strains of bacterial and viral diseases (bird flu) -horizontal gene transfer (between species)

  38. Linkage: Summary Recombination: generates new combinations (inter and intrachromosomal) Genetic maps: - genes linked on the same chromosome - location of new genes relative to genes already mapped

  39. Linkage: Summary Hunting for genes (Human Diseases) - genetic markers: DNA variation - co-inheritance with diseases using pedigree information - recombinants used to estimate linkage - MUN Medical Genetics

  40. Extensions to Mendelian Genetics Ch. 14 From Gene to Phenotype Readings: Ch. 14 p. 454 – 473 Problems: Ch. 14: 2, 3, 4, 5, 6, 7

  41. Chapter 1 Genes, environment, organism Phenotype = gene + env. + gene x env. + gene x gene Mendelian Genetics: Genotype Phenotype Dominance ?

  42. G x E interaction

  43. Extensions to Mendelian Genetics (Gene  Phenotype) 1. Dominance 2. Multiple alleles 3. Pleiotropy 4. Epistasis (gene interaction) 5. Penetrance and expressivity

  44. Gene interaction Alleles at one gene Dominance Different genes Epistasis

  45. 1. Dominance Location of heterozygote between two homozygotes 1. Complete 2. No dominance 3. Incomplete (partial) 4. Codominance

  46. Homozygotes: A1A1 A2A2 Heterozygote: A1A2

  47. Incomplete Dominance red white pink

  48. Codominance Human Blood Groups: Genotype Phenotype** AA A AB AB co-dominance BB B ** antigen protein on RBC

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