Announcements for MCB 110L Office Hours (starting Mon., 28 Jan.): M 12-1 PM Jane GPB 203 Tu 2-3 PM Dale GPB 109 W 12-1 PM Jesse GPB 201 W 12-1 PM Maumita GPB 203 F 12-1 PM Joo Eun GPB 203 Th 3-4 PM Jeremy 526 Barker

Life Cycle of the Budding Yeast, Saccharomyces cerevisiae

Genetic Nomenclature Conventions for Saccharomyces cerevisiae Normal (“wild-type”) locus: YFG1 Loss-of-function (hypomorphic) allele: yfg1-1 (point mutation) yfg1-∆1 (null mutation) Gain-of-function (hypermorphic) allele: YFG1-20 Alteration-of-function (neomorphic) allele: YFG1-54 A normal, hypermorphic or neomorphic allele is dominant over a hypomorphic allele: YFG1/yfg1 Presence and status of an episome or non-Mendelian determinant in brackets: [YCp352], introduced DNA plasmid [cir+], endogenous 2 m DNA circle [rho-plus = +], functional mitochondrial DNA [psi+], presence of prion form of Sup35 (yeast eRF3) [KIL-k1], endogenous dsRNA viroid encoding secreted toxin

Strain YSA1: MAT fcp1∆::LEU2 TRP1:: fcp1-2ts ade2 FCP1 [TFIIF-associated Rpo21 carboxy-terminal domain (CTD) phosphatase] Strain YSA1: MAT fcp1∆::LEU2 TRP1:: fcp1-2ts ade2 his3 leu2 trp1 ura3 [YCp-FCP1, URA3] The FCP1 gene is essential for S. cerevisiae cell viability. (mutations in the orthologous human gene product, CTDP1, causes congenital cataracts with facial dysmorphism and neuropathy)

The Concept of a Genetic Cross e.g., MATa mutation a X MAT mutation b What can we learn from such crosses? • Assess whether mutation a is dominant or recessive to the corresponding WT locus, and assess whether mutation b is dominant or recessive to the corresponding WT locus (dominance test) • Determine whether mutation a and mutation b are likely to be alterations of the same gene (complementation test) • Map the relative positions of locus a and locus b by examining their segregation behavior in meiosis (tetrad analysis) • Generate a potentially useful double mutant (epistasis test)

MATa MAT

CEN3 642 bps 747 bps a haploid:  haploid: a/ diploid:

MAT2 = YCR039c MAT1 = YCR040w MATa1 = no ORF no. a1 a

A B C D E F G H I J K M N O L P

Systematic name for the FCP1 locus is YMR277w. Automatically tells you that the ORF encoded by the FCP1 gene is situated on the right arm of Chromosome XIII and transcribed in the direction away from CEN13.

MAT2 = YCR039c MAT1 = YCR040w MATa1 = no ORF no. a1 a

Available from Cold Spring Harbor Laboratory Press

The Concept of a Genetic Cross e.g., MATa mutation a X MAT mutation b What can we learn from such crosses? • Assess whether mutation a is dominant or recessive to the corresponding WT locus, and assess whether mutation b is dominant or recessive to the corresponding WT locus (dominance test) • Determine whether mutation a and mutation b are likely to be alterations of the same gene (complementation test) • Map the relative positions of locus a and locus b by examining their segregation behavior in meiosis (tetrad analysis) • Generate a potentially useful double mutant (epistasis test)