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