Origin of variegated endosperm: differential loss of markers

break

“healed” broken chromosomes

New telomeres in yeast are initiated with a highly 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

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

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 a a leu2 strain ura3 . . . 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 colonies are red 1 SUP11 colonies are pink 2 SUP11 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