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
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
a haploid:
 haploid:
a/ diploid:
747 bps
a
MATa1 = no ORF no.
a1
MAT2 = YCR039c
MAT1 = YCR040w
a1
a
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
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.
a
MATa1 = no ORF no.
a1
MAT2 = YCR039c
MAT1 = YCR040w
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)