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Origin of variegated endosperm: differential loss of markers
break
“healed” broken chromosomes
Kramer KM, Haber JE
New telomeres in yeast are initiated with a highly
selected subset of TG1-3 repeats.
Genes Dev 1993 7:2345-56
HO endonuclease
In a rad52 diploid, repair of the DSB by new telomere addition
near, but often not at, T2G4 Tetrahymena repeats
in 16 events at sites ending in GTGG, the first TG1-3 nucleotides added always included
either an 11- or a 13-bp sequence (GTGTGGGTGTG or GTGTGTGGGTGTG), after
which each new telomere diverged into a less ordered TG1-3 pattern.
When TLC1 (telomerease RNA) was cloned, this proved to be the template sequence)
DHFR amplification in response to methotrexate
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Cell, Vol. 89, 215–225, April, 1997
Expression of Fragile Sites Triggers Intrachromosomal Mammalian Gene Amplification and Sets Boundaries to Early Amplicons
Arnaud Coquelle 1, Eva Pipiras 1, Franck Toledo 1, Gérard Buttin 1, and Michelle Debatisse 1
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p53 defective cells don’t eliminate cells with broken chromosomes by apoptosis
Chromosome instability mutations in yeast chl, ctf, ipl, cin
Identify
centromere and spindle pole body components
microtubule elements
Ipl1 (Aurora) kinase
cohesins
MATa
MATa/MATa (non-mater)
2n-1 chromosome loss
MATa
a a leu2
strain
ura3
.. .
a a leu2
chl1
strain
ura3
a strain
ura3
Mitotic Stability of Yeast Chromosomes: a Colony Color Assay
That Measures Nondisjunction and Chromosome Loss
P. Hieter , C. Mann , M. Snyder , and R. W. Davis
Cell 40:381-392 (1985)
An alternative, but similar strategy: a CEN plasmid carrying SUP11, a
weak ochre supressor in a strain carrying ade2-101 (an ochre mutation)
No SUP11
1 SUP11
2 SUP11
colonies are red
colonies are pink
colonies are white
1:0 segregation
(chromosome loss)
2:0 segregation
(nondisjunction)
Strain: ade3 ade2 ura3 leu2
ade3 ade2 is white ADE3 ade2 is red