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Exercise 3: Mendelian Genetics

Exercise 3: Mendelian Genetics

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Exercise 3: Mendelian Genetics

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  1. Exercise 3: Mendelian Genetics

  2. Objectives (see page 27) • Crosses • Monohybrid Autosomal and Sex-Linked • Dihybrid Autosomal • Punnett Squares • Scientific Method • Chi-squared test • Drosophila and Pea Genetics

  3. When Meiosis goes afoul…

  4. Karyotype: Trisomy 21

  5. From Meiosis to Mendel • Meiosis produces haploid (n) gametes • Only 1 chromosome of each type (homologue) • Mendelian genetics concerns the recombination of these chromosomes

  6. Allele: One of two or more molecular forms of a gene that code for different versions of the same trait P p

  7. Genotype dictates Phenotype • P=purple • dominant • p=white • recessive

  8. True Breeding Individuals: Genetic line always produces same type of progeny when crossed within the line Homozygous Homozygous

  9. Gregor Mendel (1822-1884)

  10. Results Cross F1

  11. How?? Started with truebreeders • F1 Generation • All Heterozygous • F2 Generation • Determine probability of each genotype and Phenotype • Punnett square

  12. F2 Genotype and Phenotype Ratios

  13. ww Ww W? ww Ww ww Ww Ww ww Ww Ww W? W? Pedigrees

  14. Dihybrid Cross and Independent Assortment

  15. Problems with Mendel’s Laws • Environmental influences

  16. Problems cont • Not all traits are independently assorted • Pleiotropy: 1 gene  Many traits • Epistasis: Many genes  1 trait

  17. Problems cont • Multiple Alleles • ABO • AB codominant

  18. Problems cont • Incomplete dominance

  19. Sex-linked Traits • Located on the X chromosome • Females XX, Males XY • Other chromosomes are AUTOSOMAL

  20. Today’s Lab: Computer Simulation • Monohybrid crosses • Autosomal or Sex-linked • Use reciprocal cross • Dominant or recessive • Dihybrid crosses • Dominant or recessive • Test with Chi-square statistical test

  21. Describe Phenomenon Formulate Falsifiable Hypotheses to Explain the Phenomenon Design and Implement Tests of Hypotheses Analyze Results (statistics) Draw Conclusions and/or Modify Hypotheses Classical Scientific Method