Welcome to Bio 290, Introduction to Genetics!

1. Welcome to Bio 290,Introduction to Genetics!

2. Today’s Agenda: • In-Class Assignment 2 • Group Discussion about Gene Therapy Paper • Introduction to Independent Assortment of Genes (Ch 3) • Poster Project-Identify topic and decide if you will work in groups

3. Why is it important to understand independent assortment of genes? • In agriculture? • In animal breeding? • In genetics research?

4. What does independent assortment mean? • Chromosome pairs act independently at meiosis • Alleles of the heterozygous gene pairs show an “independent assortment”

5. Mendel’s peas again… • He performed a dihybrid cross • Used the genes for seed shape and seed color

6. Mendel crossed two homozygous dihybrids • What is the expected genotypes of the F1? • What is the expected phenotype if the F1 is selfed?

7. Mendel’s 2nd Law (Principle of Independent Assortment) • He concluded that different gene pairs assort independently in gamete formation • What type of genes would not follow this law?

8. Predicting ratios of progeny: Branch diagrams • Perform a dihybrid cross of self A/a;B/b • How many different genotypes? • How many different phenotypes?

9. Statistical approach to predicting progeny is easier • Product rule: Probability of independent events both occurring together is the product of individual probabilities • Ex: What is the probability that I can roll a “6” on two dice?

10. Statistical approach to predicting progeny is easier • Sum rule: Probability of either two mutually exclusive events occurring is the sum of their individual probabilities • Ex: What is the probability of rolling two 5’s ortwo 6’s?

11. What is the chi-squared test? • Statistical analysis to compare predicted ratios to an actual observed ratio…to determine if a hypothesis is correct

12. An example • You have a jar with 200 marbles, 100 of them are red and 100 of them white. You remove 100 marbles • What ratio would expect of red:white? • How can you interpret that you actually have 60 red and 40 white….

13. Use Chi-squared • χ2 = Σ (O − E)2/E • for all classes in which E is the expected number in a class, O is the observed number in a class, and Σ means sum of.

14. Reference Chi squared chart

15. Why are pure lines important? • What types of alleles are expressed if a monohybrid (A/a) is selfed? • What happens over more successive generations?

16. What is meant by hybrid vigor? • When two lines are united in an F1 hybrid, hybrid shows greater size and vigor • First seen with corn….any other examples?

17. Independent assortment of chromosomes

18. Independent Assortment in diploid organisms

19. Stages of Neurospora cross

20. Meiosis in Neurospora • Meiosis followed by mitosis results in 8 ascospores

21. Meiotic Recombinants? • Why is this important?

22. Polygenic Inheritance • Can you think of any examples of characteristics that exhibit a lot of variation?

23. Polygenic Inheritance • Progeny of dihybrid self can be expressed as additive allelic “doses”

24. Organelle Genes

25. How are organelles inherited? • Remember the composition of the egg and sperm?

26. What is cytoplasmic segregation?

27. Pedigree of mtDNA disease

28. Reminders for Next Week • Agriculture Paper - Start Reading! (Pre-class assignment on Review Paper due Thursday at 2) • Read Chapter 3: Focus on key points we’ve identified today to help you prepare for the Quiz • Quiz 3- Posted by Monday at noon, due by Wednesday at noon. • Don’t forget to use our fabulous Discussion Room!