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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 overa 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

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)

FCP1 [TFIIF-associated Rpo21 carboxy-terminal domain (CTD) phosphatase]

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 thecorresponding WT locus, and assess whether mutation bis dominant or recessive to the corresponding WT locus(dominance test)

• Determine whether mutation a and mutation b are likely to bealterations of the same gene (complementation test)

• Map the relative positions of locus a and locus b by examiningtheir segregation behavior in meiosis (tetrad analysis)

• Generate a potentially useful double mutant (epistasis test)

MATa

MAT

CEN3642 bps642 bps

747 bps747 bps

a haploid:

haploid:

a/ diploid:

MAT2 = YCR039c

MAT1 = YCR040w

MATMATaa11 = no ORF no. = no ORF no. a1

a1

a

a

AB

CD

EFGHIJ

K

MNO

L

P

Systematic name for the FCP1 locus is YMR277w.

Automatically tells you that the ORF encoded bythe FCP1 gene is situated on the right arm of Chromosome XIII and transcribed in the directionaway from CEN13.

MAT2 = YCR039c

MAT1 = YCR040w

MATMATaa11 = no ORF no. = no ORF no. a1

a1

a

a

Available fromCold Spring

Harbor LaboratoryPress

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 thecorresponding WT locus, and assess whether mutation bis dominant or recessive to the corresponding WT locus(dominance test)

• Determine whether mutation a and mutation b are likely to bealterations of the same gene (complementation test)

• Map the relative positions of locus a and locus b by examiningtheir segregation behavior in meiosis (tetrad analysis)

• Generate a potentially useful double mutant (epistasis test)