Introduction to Yeast Genetics

1
Introduction to Yeast Genetics
Kathy Friedman Office Room 2417 Stevenson
Center Phone [phone] Email
katherine.friedman_at_vanderbilt.edu
Please print and bring these notes to class.
We will fill in the blanks during the lecture
http//saturn.roswellpark.org/huberman/BIR572/Yeas
tGeneticsLectureNotes.html
2
Yeast as a Model Organism
Easily manipulated
Rapid growth (1.5-2.5 double)
Non-pathogenic
Stable haploid and diploid forms
Simple mating strategies
Efficient transformation
Efficient homologous recombination
Visible cell cycle
3
Yeast Life Cycle
4
How is mating type determined?
5
What happens when a and a cells meet?
6
Yeast cells can switch mating type
HML
HMR
MAT
a
a
a
cen
Homothallic strains
Heterothallic strains
7
Wild yeast are PROTOTROPHIC...
Yeast laboratory strains are AUXOTROPHIC...
A
B
C
D
E
Uracil
8
Yeast Nomenclature
URA3
ura3
ura3-52
ura3-55
ura3D
yfg1URA3
Ura3p
9
Auxotrophic markers can be used to
distinguish mating type of yeast
Mystery strains A, B, and C
a and a testers
MATa ura3 his3 trp1
MATa phe1
MATa ura3 his3 trp1
MATa phe1
MATa/MATa ura3/ura3 ade2/ade2
10
Auxotrophic markers can be used to
distinguish mating type of yeast
Mystery strains A, B, and C
a and a testers
MATa ura3 his3 trp1
MATa phe1
MATa ura3 his3 trp1
MATa phe1
MATa/MATa ura3/ura3 ade2/ade2
A
B
C
Aa
Ba
Ca
a
Aa
Ba
Ca
a
Rich Media
Minimal Media
11
Yeast package their meiotic products
Meiosis I
Meiosis II


-
-
12
Spores can be separated by micromanipulation
from Getting Started with Yeast by Fred Sherman
13
Segregation of an auxotrophic marker
from Getting Started with Yeast by Fred Sherman
14
What if two genes are independently assorting?
AB x ab
Tetrad type
AaBb
15
How do the tetrad types arise?
16
Calculating Distance to Centromere
??
YFG
TRP1
TRP1
YFG
??
yfg
trp1
trp1
yfg
IF one gene is known to be centromere linked
17
Example
trp1 ade4
TRP1 ADE4
PD
24
NPD
26
TT
10
60
18
What if the two genes are linked?
Recombinant/Total map distance
19
What are the consequences of double recombination?
from Getting Started with Yeast by Fred Sherman
20
Accounting for double recombination
Map distance (1/2SCO DCO)/total tetrads x
100
Assumptions
21
Example
Dissect 100 tetrads to calculate distance between
leu and spu
PD
56
NPD
3
TT
41
100
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How do we find mutations in the process of
interest?
Selection
Screen
Enrichment
23
To Mutagenize or not to Mutagenize
Spontaneous mutation rate 2-12 x 10-6 per gene
per generation
Advantages of mutagenizing
Disadvantages of mutagenizing
24
How do you determine if the phenotype is due to
mutation in a single gene?
25
The importance of backcrossing
abcd x ABCD
26
Dont forget to transfer your mating mixtures to
the appropriate spots on the minimal plate!
Let the plate grow at room temperature for the
next two days. Well vote on the identity of
each strain on Friday.