crossing over.txt

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Author:
rincrocci
ID:
150982
Filename:
crossing over.txt
Updated:
2012-04-29 18:50:17
Tags:
crossing over
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Description:
crossing over
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  1. Holliday vs. Meselson-Radding Models
    • Holliday model: SYMMETRIC formation of heteroduplex DNA on BOTH chromatids
    • Meselson-Radding: ASSYMETRIC recombination >>> leads to Assymetric heteroduplex DNA
  2. Recombination steps
    • 1. Synapsis of chromosomes
    • 1. Double Strand BREAK Formation
    • 2. 5’ resection
    • 3. Unstable strand invasion
    • 4. Repair synthesis and Holliday Jxn
    • 5. Crossover/Noncrossover
  3. Role of spo11
    • Transesterase protein involved in meiosis
    • Aids in recombination through Double stranded breaks
    • These breaks aid in FORMING crossovers
    • *Mre11 ENDONUCLEASE involved in cleaving of DS DNA also
  4. Failure to form crossover consequences
    • 1. No homologue pairs formed
    • 2. No aligning at metaphase plate
    • 3. No SEGREGATION during meiosis
  5. Double Stranded break
    • 1. Spo11 attached on one end, with other end with a free 3’ tail
    • 2. Spo11 is released, taking with it 2 oligonucleotides, called spolligos
    • 3. Once Spo11 released, the other end has a free 3’end tail as well
  6. Role of Rad51
    • Involved in homology search to IDENTIFY homologous chromosomes
    • Also role in REPAIR of damaged DNA
    • Assembles on other side of DSB as the Dmc1
  7. Role of Dmc1
    • Initiates stable STRAND INVASION
    • Assembles on 3’ tail of a ssDNA break
  8. Role of Mnd1-Hop2 in homologous recombination
    • Stabilizes interactions between homologous chromosomes
    • Localizes to chromosomes independent of Dmc1 and Rad51
  9. Synapsis Initiation complex (SIC)
    • Mediates synapsis, pairing and recombination
    • Found B/w homologous chromosomes during replication
    • Contain Zip1-3, which promote polymerization

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