1. שיטות מיפוי נוספות תדירות רקומבינציה מהכלאה עצמית
שימוש בכרומוזום Y כ-'בוחן'
"הגבול" בין תאחיזה להפרדה עצמית – 2 C
התחשבות בשיחלופים שלא רואים – "mapping function”
טטרדות – מיוזות בודדות, ומיפוי בין גן לצנטרומר

4. =Budding Yeast =Bakers Yeast
The yeast Saccharomyces cerevisiae is commonly used
as a model system
=Budding Yeast =Bakers Yeast

5. The yeast Saccharomyces cerevisiae is clearly the most ideal
eukaryotic microorganism for biological studies. The "awesome
power of yeast genetics" has become legendary and is the
envy of those who work with higher eukaryotes. The complete
sequence of its genome has proved to be extremely useful as
a reference towards the sequences of human and other
higher eukaryotic genes. Furthermore, the ease of genetic
manipulation of yeast allows its use for conveniently analyzing
and functionally dissecting gene products from other eukaryotes.
--Fred Sherman

6. Major characteristic of the budding yeast
Unicellular Eukaryote
Grows by budding
16 linear chromosomes
Generation Time: ~100 min
Can exist as stable diploid or haploid

7. Major advantages of the budding yeast as a genetic system
Grows fast
Cheap
Compact genome, fully sequenced since 1996.
Easy to handle
Superb Genetics, Biochemistry, Molecular Biology
Easy to transform, high efficiency of gene targeting

8. Yeast: A model eukaryote
Lee Hartwaell
Paul Nurse
Tim Hunt
"for their discoveries of key regulators of the cell cycle"
The Nobel Prize in Physiology
or Medicine 2001
Yeasts – the ultimate model eukaryote for unicellular issues and some basic cell-cell interactions
Yeast studies have broken new ground in:
Cytoskeleton functions transcription mechanisms**
cell cycle** transcriptional regulation
organelle biogenesis chromatin modification
secretion* signal transduction
protein targeting mechanisms protein degradation*
chromosome replication DNA repair
genome dynamics retroviral packaging
prions recombination mechanisms
ageing function of new genes
metabolism protein modification
*Lasker Award **Nobel Prize
The Nobel Prize in Physiology or Medicine 2016
Yoshinori Ohsumi
The Nobel Prize in Physiology or Medicine 2016 was awarded to
Yoshinori Ohsumi "for his discoveries of mechanisms for autophagy".
The Nobel Prize in Physiology
or Medicine 2013
for their discoveries of machinery regulating vesicle traffic,
a major transport system in our cells
James E. Rothman
Thomas C. Südhof
Randy W. Schekman

9. What is yeast?
Yeast - a fungus that divides to yield individual separated cells (as opposed to molds- mycelium)
Saccharomyces cerevisiae (budding yeast)
baker’s yeast closely related to brewer’s yeasts grows on rotting fruits
Schizosaccharomyces pombe (fission yeast)
African brewer’s yeast
Saccharomyces relatives
(S. bayanus, S. paradoxus, etc.)
Candida albicans
Cryptococcus neoformans

10. Yeast life cycle

11. Yeast cell cycle (mitosis)
Major control
point is at G1/S
morphology reflects cell cycle position
same in haploids and diploids
major control point is ‘start’--
cells can choose mitosis, meiosis or mating
depends on ploidy, env. & presence of partner
Morphology + nuclear localization and MT
localization indicates the
precise stage of the cell cycle

12. ura3- Diploid Meiosis ura3- ura3- ura3- strain WT strain Mating URA3+

14. Mendel’s rules are relevant for organisms that sexually reproduce: diploid/haploid
Plants, Animals, many More…
Those that ‘do’
meiosis

16. Diploid
Mitosis
Haploid
Mitosis

17. Of diploid 1n 2 1
Of haploid

18. Centromere mapping

21. Centromere mapping
Nonsister chromatids do not cross over
First-division segregation pattern or MI pattern

22. Centromere mapping
Nonsister chromatids cross over
Second-division segregation pattern or MII pattern

23. Second-division MII segregation

32. 1. The loci are on separate chromosomes
2. The loci are on opposite sides of the centromere
on the same chromosome
3. The loci are on the same side of the centromere

33. Unordered tetrads BA ba Ba bA BA Ba ba bA NPD PDT TT B B b b B B b b a
Mating b A b A
Heterozygous diploid
Tetrad B a
Meiosis B a b A b A BA ba Ba bA BA Ba ba bA
Tetrad Dissection
NPD
PDT TT

34. Yeast tetrad analysis (classic method)
Step1: separate spores by micromanipulation with a glass needle
tetrad
Step2: place the four spores from each tetrad in a row on an agar plate
Step3: let the spores grow into colonies

35. Classical approach (tetrad dissection)BA ba Ba bA BA Ba ba bA
Tetrad Dissection
NPD
PDT TT
Tetrad
bni1∆ bnr1∆

37. Map distance=50(T+6NPD) m.u
MESSAGE
Linear and unordered tetrads can be used to calculate the frequencies of single and double crossovers, which can be used to calculate accurate map distances.
Perkin formula
Map distance=50(T+6NPD) m.u

38. BA ba Ba bA BA Ba ba bA NPD PDT TT
What PD, NPD and T values are expected when dealing with unlinked genes? B b B
Mating b a a a A a a a A
Tetrad
Meiosis B a a B a a b a A b A
Heterozygous diploid BA ba Ba bA BA Ba ba bA
Tetrad Dissection
NPD
PDT TT

39. BA ba Ba bA BA Ba ba bA NPD PDT TT
What PD, NPD and T values are expected when dealing with unlinked genes?
The sizes of the PD and NPD classes will be equal as a result
of independent assortment.
The T class can be produced only form a crossover between the
specific loci and their respective centromeres B b B
Mating b a a a A a a a A
Tetrad B a a
Meiosis B a a b A b A
Heterozygous diploid BA ba Ba bA BA Ba ba bA
Tetrad Dissection
NPD
PDT TT

40. שיטות מיפוי נוספות תדירות רקומבינציה מהכלאה עצמית
שימוש בכרומוזום Y כ-'בוחן'
"הגבול" בין תאחיזה להפרדה עצמית – 2 C
התחשבות בשיחלופים שלא רואים – "mapping function”
טטרדות – מיוזות בודדות, ומיפוי בין גן לצנטרומר

41. A formula that relates RF values to the “real” physical distance
Haldane’s mapping function
A formula that relates RF values to the “real” physical distance

42. Any number of crossovers produces a frequency of 50%
Haldane’s mapping function
Any number of crossovers produces a frequency of 50%
Recombinants within those meiosis
The true determinant of RF is the relative
sizes of the classes with no crossovers,
versus classes with any nonzero
number of cross overs

43. The larger m get e-m tends to 0
התחשבות בשיחלופים שלא רואים – "mapping function”
The larger m get e-m tends to 0
and RF tends to 1/2 , or 50m.u
A formula that relates RF values to “real” physical distance
m-is the mean number of cross overs that occur in a segment per meiosis

46. התחשבות בשיחלופים שלא רואים – "mapping function”

47. of map distance can be circumvented by the use of map function
MESSAGE
The inherent tendency of multiple crossovers to lead to an underestimate
of map distance can be circumvented by the use of map function
(in any organism), and by the Perkin formula
(in tetrad-producing organisms such as fungi)