1. Genetics can be used to characterize biological pathways Epistasis tells which gene products are involved in common pathways and which act earlier or later in a process. Complementation tells us if variation is due to mutations in one gene or several genes.

2. What are the relationships between color types? Purple is dominant to white A X purple RR white A rr purple Rr Relationship between 2 chosen color variants

3. F2 1 RR, 2Rr and 1rr X Purple is dominant to White1 purple RR white A rr F1 X purple Rr

4. Punnet square r r rr Female gametes Male gametes R R RRRr

5. What are the relationships between color types? Purple is dominant to red X purple RRPP Purple RrPP or RRPp Red rrPP or RRpp

6. Complementation test Red and white A are caused by mutations in different genes X white A rrPP Purple RrPp red rrPP or RRpp Cross two recessive mutants to determine if the mutations are in one gene or more than one.

7. Epistasis Two genes for flower color Are they two steps in the same pathway to make pigment? Where are the two genes in the pathway?

8. 1. Purple is either a mixture of blue and red pigments each made in a separate biochemical pathway. or 2. Purple results from modification of the same precursor from a white precursor to a red intermediate and finally a purple pigment. We can use genetics to distinguish the two possibilities. The effect of variant alleles in multiple genes that affect pigment in combination will answer the question.

9. Precursor 1 Precursor 2 Blue Red Precursor 1 R P Red R P Purple Pathway 1 Pathway 2 Coexpression of blue and red pigment derived from different precursors makes purple. Modification of the same precursor leads to first a red pigment and then a purple pigment

10. Epistasis test X White A rr Purple Rr Pp Red pp Start with complementation test: Cross two recessive mutants to determine if the mutations are in one gene or more than one.

11. Epistasis test part 2 X Purple F1 Rr Pp Cross F1 plants from the complementation test And follow how the different alleles segregate in the F2 generation. Purple F1 Rr Pp ?

12. Punnet Square: two genes with randomly segregating alleles Male gametes Female gametes RP Rp rP rp rPRpRP RRPP RRPp RrPPRrPp RRpp RrPpRrpp RrPPRrPprrPP rrppRrPpRrpprrPp 9R_P_ 3R_pp 3rrP_ 1rrpp RrPp X RrPp

13. Precursor 1 Precursor 2 Blue Red R P If Pathway 1 Coexpression of Blue and red pigment derived from different precursors Makes purple 9R_P_3R_pp3rrP_ 1rrpp Phenotypes: purplewhiteredblue Recessive alleles Lead to lack of either Red or blue pigment

14. Relationship between white a and red X X white A rrPP red RRpp F1 is all purple RrPp F2 9 43

15. F2: 9R_P_ 3R_pp3rrP_ 1rrpp Phenotypes: purplewhiteredwhite rr - get no red precursor neither purple nor red pigment can be made pp – can get red pigment if correct R alleles are present but not purple Precursor 1 Red R P Purple Pathway 2 Modification of the same precursor leads to first a red pigment and then a purple pigment

16. R is epistatic to P Mutations in the R gene cover the effect of mutations in the P gene. This is because R is upstream of P in a biological pathway The P protein requires the wild type function of the R protein. R can be a regulator required to activate expression of P or R can be an enzyme upstream in a biochemical pathway

17. Using multiple allelism tests with diverse recessive mutants, We can identify all the genes specifically involved in making the purple pigment

18. Genetics can be used to determine the order of steps in a biological pathway Epistasis tells which gene products are involved in common pathways and which act earlier or later in a process.

19. Mouse as a model for mammalian genetics

20. Origins of Mouse Genetics Early domestication by Greeks and Romans Chinese and Japanese fondness for unusual-looking mice Early 19th century-popular objects of fancy in Europe Early 20th century-English and American mouse fanciers Early pioneers included LC Dunn, Clarence Little, Sewall Wright, and George Snell

21. Why Mice As an Experimental Organism? Short life cycle Easily bred High fecundity Hardy Requires little space Large amount of phenotypic variation Easy to genetically engineer Mammalian species

22. Evolutionary Relationships 0 myr bp 1002003004005006007008009001000 C. elegans D. melanogaster Xenopus Mice Humans

23. A mouse is not a mouse is not a mouse Hundreds of strains Great phenotypic diversity Variation exceeds that in the human population

26. Why is there biological concordance for human and mouse Evolutionary conservation!! genome (gene content, arrangement and sequence) structure (gross and molecular anatomy) function (physiology and molecular circuits) regulatory systems

27. Why is there biological concordance for human and mouse Evolutionary conservation!! Important loci represent a finite set of key regulatory genes “Key” means location in the regulatory network (nodes)

28. Engineered Models Allows controlled experimental testing of specific genes specific environmental conditions or exposures Ideally suited to test specific hypothesis generated from human population studies or other laboratory findings

29. Engineered Models Transgenics usually used to over-express genes can be global or tissue-specific can be temporally regulated Knockouts/knockins usually used in inactivate genes can be global or tissue-specific can be temporally regulated can introduce genes into a foreign locus can make amino acid modifications

30. UV Mutagenesis in Yeast Geneticists need variation to study the function of gene products. We create variation in the laboratory by mutagenesis

31. Fig. 7.2

32. Fig. 7.6

33. Fig. 7.12b1

34. Fig. 7.12b2

35. By choosing the correct mutagens, we can control the type of mutations we make

36. Fig. 7.7

37. Photoreactivation requires photolyase enzyme

38. Mutagenesis of yeast haploid Irradiate with UV. Calculate survival curve Select optimal dose for isolation of mutations. Select on appropriate selective media: Replica plating to identify nutrient deficiencies.