Tetrad analysis
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Tetrad analysis ססססס ססססס/ססס/סססס ססססס ססססס
description
Tetrad analysis. אסקוס. ספורה/נבג/תוצר מיוזה. טטרדה. Replica plating. Replica plating. -URA. -TRP. -ADE. -LYS. YePD. URA3 TRP1 ade2 lys2. URA3 trp1 ade2 lys2. ab X a + b +. A. B. a. b. A. B. A. b. A. B. A. b. a. b. a. B. a. b. a. B. PD. =. NPD. A. B. A. B. - PowerPoint PPT Presentation
Transcript of Tetrad analysis
Tetrad analysis
אסקוס
/ מיוזה/ תוצר נבג טטרדהספורה
Replica plating
Replica plating
YePD
-ADE
-URA
-TRP
-LYS
URA3 TRP1 ade2 lys2
URA3 trp1 ade2 lys2
ab X a+b+
A
a
B
b
PD
A
a
A
a
B
b
B
b
A
a
A
a
b
B
b
B
NPD=
A B
a b
A B
a b
A B
a bA B
a b PD only
A B
a b
X
A B
a b
A b
a B
TT
Thus RF=1/2TT
הכפולות הרקומבינציות עם מה ?אבל
מכך ויתרה כפולות רקומבינציות כולל אינו הקודם החישוב כלומרה כי מטעה כפולות TTהוא גם ....כולל
Assuming that, in our hypothetical cross of a+ b+ × a b, the observed frequencies of the ascus classes are 56 percent PD, 41 percent T, and 3 percent NPD. Using the formula, we find the map distance between the a and b loci to be:
Let us compare this value with that obtained directly from the RF. Recall that the formula is:
In our example,
This RF value is 6 m.u. less than the estimate we obtained by using the map-distance formula because we could not correct for double crossovers in the RF analysis.
SummaryPD=NPD - No linkage
PD only high linkage maybe the same gene
PD>TT>NPD -Linkage
RF=1/2(TT+6NPD)
Repair, and Recombination
• E. Coli SOS system
Emergency response that allow the insertion of non specific base!
In bacteria its DinB, UmuC and UmuD that encode for pol IV and V, the error prone polymerase that incorporate an arbitrary base across to the damaged base.
Pol eta/iota
Direct reversal By photolyase
Base excision repair
• Start with glycosylase that break the sugar-base bond* and release the altred base and generating apurinic or apyrimidinic sites.
* For example guanine +EMS -> 0-6-ethylgunine (can mispaired with Thymine)
Nucleotide excision repair (NER) in bacteria
Nucleotide excision repair (NER) in yeast
XPD and XPB – helicaseXPG and XPF - endonuclase
Cockayne syndrome
• Mutation in CSA or CSB causes to retinal degeneration, hearing impairment, ataxia and photosensitivity
• Die very young
Tricothiodystrophy (TTD)
• Mutations in XPD
WT
TTD
Human shows photosensetivity, brittle hair, skin defects and short life span.
XPD -/- mice show also wasting, scoliosis, osteophoresis and melanocyte loss.
WT TTD
3m
15m
Mismatch repair in bacteria
Mismatch repair (NER) in human
Spo11
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Aberrant ratio
4:4 6:2 2:6 5:3 3:5
Gene conversion
