1. Rules: Cell phones off Computers only for class related work No food or drink in lab room Text Book: Hartwell et al., 2nd Edition 2004 Genetics from Genes to Genomes Mc Graw-Hill, Boston. Web page: www.bio.unc.edu/courses/2006Fall/Biol423L Biol 423L Laboratories in Genetics

2. Goals for course: Reinforce basic genetic principles Introduce model organisms commonly used by geneticists Learn how genetics is used to understand Disease Biochemical pathways Development

3. Lab reports: Abstract Introduction Results Discussion Course information page has instructions about preparing your lab reports.

4. Grading: Lab Reports: 50% of grade 5% of that is participation 1 day late, 50% off more than that will only be graded under special circumstances. Research Paper: 10% of grade Topics due Oct. 9. Outline due Oct. 23. Paper due Nov. 29 2 quizzes: 10% each of final grade. Oct. 2 and Nov. 13. Final exam: 20% of final grade comprehensive Dec. 11.

5. Genes Alleles and Epistasis

6. Genetics starts with observation Use genetics to understand the cause of the variability. What proteins or RNAs are responsible for the variability you can see? Observe variability

7. Easy example, flower color

8. How many genes affect flower color? How variable are the proteins encoded by those genes? What is the pathway to make flower color?

9. List of terms: Trait: some aspect of an organism that can be observed, measured Phenotype: the way a trait appears in an individual, the combination of genotype and environment. Genotype: the constitution of alleles at any gene in an individual. Gene: continuous stretch of DNA sufficient to encode a messenger RNA or a functional RNA. Locus: A region of a chromosome, usually for a single gene. Messenger RNA: the RNA message for a single protein. Allele: a variant of the sequence of a given gene. Diploid: an individual with two copies of each chromosome. Haploid: an individual with one copy of each chromosome.

10. How many genes affect flower color? How variable are the proteins encoded by those genes? What is the pathway to make flower color?

11. First make sure the types are heritable and true breeding (homozygous for flower color alleles) X purple by purple (self) All uniform Homozygous: a diploid individual with two copies of the same allele for a given gene. Heterozygous: a diploid individual with two different alleles for a given gene.

12. What are the relationships between color types? Purple is dominant to Red X

13. What are the relationships between color types? Purple is dominant to white X

14. Complementation tests can be made between recessive alleles. A dominant allele cannot be used. Why? 1. How many genes are required to make purple pigment in flowers?

15. Allelism test: Cross different white flowered plants If the mutations are in the same gene, The progeny will be white White 1 X

16. Allelism test: Cross different white flowered plants If the mutations are in different genes, The progeny will be pigmented White 1 X White 2

17. Allelism or complementation test If plants with recessive alleles are crossed and the progeny also have the recessive trait, The alleles are variants of the same gene If plants with recessive alleles are crossed and the progeny have the dominant trait, The alleles are variants of different genes

18. Precursor 1 Intermediate White1 White2 Purple Pathway to purple

19. White 1 White 2 X Purple rrAARRaa RrAa

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

21. Genetics can be used to determine the Order of steps in a biological pathway Epistasis tells which gene products act earlier or later in a process.

22. What are the relationships between color types? Purple is dominant to White 1 X

23. F2 1 RR, 2Rr and 1rr X Purple is dominant to White1 Purple RR White1 rr F1 X Purple Rr

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

25. What are the relationships between color types? Purple is dominant to Red X PP Pp pp

26. Epistasis Two genes for flower color Two steps in a pathway to make pigment Where are the two genes in the pathway?

27. Purple is either a mixture of blue and red pigments or 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.

28. 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

29. Relationship between White1 and Red X X White1 rrPP Red RRpp F1 is all Purple RrPp F2 9 43

30. 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_pp3rrP_ 1rrpp RrPp X RrPp

31. 9R_P_3R_pp3rrP_ 1rrpp Phenotypes: PurpleWhite RedWhite Precursor 1 Red R P Purple No R - get no red precursor Neither purple nor red pigment can be made White - no pigment No P – get red pigment but not purple

32. Precursor 1 Precursor 2 Blue Red R P If Pathway 1 Coexpression of Blue and red pigment derived from different precursors Makes purple

33. 9R_P_3R_pp3rrP_ 1rrpp Phenotypes: PurpleWhite RedBlue R no P would make red pigment only No R but P would make blue pigment, Fact that loss of R changes phenotype to rr even if Functional P is expressed indicates that P and R affect a common pathway and R is before P in the pathway to make pigment.

34. Yeast complementation test for next week: Brewers Yeast Saccharomyces cerevisiae: 16 chromosomes 12,052 kb DNA 6183 ORFs About 5800 expected to encode proteins

35. Yeast is a very useful model for genetics because of its life cycle Haploid life cycle

36. Yeast is a very useful model for genetics because of its life cycle Mating cycle Diploid

37. We can isolate mutants as haploids We can test the mutations for allelism by a complementation test Two haploids are mated. The resulting Diploid has both mutations. Either the mutations are allelic and do not complement, or they are mutations in two different genes and they do complement.

38. a1 a2 Select mutants that are defective in Adenine synthesis- cannot grow without adenine in medium. Turn red on media with adenine because an adenine precursor accumulates. a1

39. a2 a1 X X a2 Which mating results in complementation?

40. Lab experiment: Corn kernels R and P RR or Rr is full color rr is no color PP or Pp are full color pp is weak color Question is pprr weak color? P epistatic to R or Is pprr no color? R epistatic to P

41. End